L96 6.0 swap into 72 longhorn. some questions

[mtdave2]

So after years of debating, I'm finally putting an LS in my ole 72 c20 longhorn. Probably putting the cart before the horse, but, now that I have the motor, I’m starting to work out what I will need to do. So I have a few questions.
Here is what I have
• L96 6.0 out of a 2018 express van 2500 with a 6l90 trans. 9k miles supper nice!
• It does have the e78 ECU (12687342)
• Has the full harness and the gas pedal.

Not as info on this motor swap, so I’m asking here to help me find the info.
1. Clearances.
a. A/C fit in the stock location? Looks like it could be tight.
b. Will the stock exhaust manifolds fit? Or must I use headers?
c. Stock oil pan work?

2. I need to have the ac work. The truck is an A/C and has currently working A/C. can the stock stuff be used and just have hoses made? Or is there a better way

3. The e78 cu, I have read there are issues getting someone who can flash the ecu. What are the options here?

4. Fuel tanks. I rebuilt and coated my stock tank behind the seat and my one saddle tank. Can I use these tanks, leave the lines to my selector valve, then put an in-line pump and filter?

5. Suggestions for motor mounts?

6. Where can I find the pinouts for this particular motor/van?

7. pedal. Anyone ever rig up something to preserve the original pedal. that is mount the pedal to the new pedal assembly.

8. where are most people mounting the ecu? in the cab under the dash? id like to see options

9. need to convert the oil and trans dipsticks from the van to the truck..what motors would use the dipsticks that would work?

There will be more, and I will make a project post of progress.
What say you? love to hear input, not so much on judgment and unhelpful comments.

[bigmoe]

8. where are most people mounting the ecu? in the cab under the dash? id like to see options.

I've heard that van wiring harnesses are a good choice because they are longer and will allow you to put the ECU in the cab. My preference would be to put it under the console (or under the bench seat) after you get it thinned.

c. Stock oil pan work?
That motor is a Gen IV right? My 5.3 is a Gen IV and the stock pan worked fine. But I'm not sure if the van pan and truck pan are the same? Find that out. If the same you can swap dipstick tube assemblies.
Truck dipstick for a 6L90 should work in yours. It's easy enough to compare the two while they're out.

[gmc684x4]

You might be able to use stock exhaust manifolds in the back engine position

Favorite choice seems to be trailblazer ss manifolds they tuck in a bit more then the silverado ones

Most headers I seen need to cut down the case for a 4l80e I would think 6l90e will be simaler

6l90 I read a bit stock that may hunt for gears I would look Into what there issues may be

[Davidf]

I used the Hooker Blackheart engine stands (with F-body mounts) and cross member. Puts the engine down low which preserves driveline angles and allows the stock low mount compressor to work without modifying anything. May need to clearance frame slightly for ps pump (because engine sits low). I’m using an in tank pump and retaining my in cab tank. I mounted the ecu on the fender behind the inner turn down…cannot see it unless you are searching for it. I used the TBSS manifolds…no clearance issues. I believe your trans will require a high hump tunnel. The 4l60e I used cleared the low hump by about 3/8”.

I asked many of the same types of questions you are asking. My advice read, read, and read some more. Most answers are out there.

[mtdave2]

[QUOTE=Davidf;8935133]I used the Hooker Blackheart engine stands (with F-body mounts) and cross member.

Which hoocker blackhearts did you use?

[Davidf]

[quote=mtdave2;8935297]

Originally Posted by Davidf

I used the Hooker Blackheart engine stands (with F-body mounts) and cross member.

Which hoocker blackhearts did you use?

There is only one choice for year and engine generation: BHS511 engine stands, fits narrow frame rail C10's. 71222024HKR-1 for the cross member that fits the 4L80.

[mtdave2]

thanks Dave.

now you said "I’m using an in-tank pump and retaining my in-cab tank"

is there a drop-in pump for those tanks? I would have to rig up 2 one for each tank. perhaps I'm misreading what you meant.

[Davidf]

Originally Posted by mtdave2

thanks Dave.

now you said "I’m using an in-tank pump and retaining my in-cab tank"

is there a drop-in pump for those tanks? I would have to rig up 2 one for each tank. perhaps I'm misreading what you meant.

I am using the GPA-2 pump from tanks inc. it will require custom bent 3/8” lines to adapt to tall and skinny tank (so pickup sits on bottom of tank). If you go this route, you will need to remove your tank, fill with water and cut access hole for pump next to level sender. You will also need split ring and gasket to mount pump assembly.

[mtdave2]

[quote=Davidf;8935308]

Originally Posted by mtdave2

There is only one choice for year and engine generation: BHS511 engine stands, fits narrow frame rail C10's. 71222024HKR-1 for the cross member that fits the 4L80.

so mine is a c20 and has the 6l90... still work?

[Davidf]

[quote=mtdave2;8935373]

Originally Posted by Davidf

so mine is a c20 and has the 6l90... still work?

Oh, missed that part…not sure. Call Holley and ask

[jjzepplin]

Congratulations and have some fun with it. Be sure to be very careful taking out the exhaust manifold bolts as they almost always break. 9000 miles is a nice find! I would replace them bolts though no matter what you use for exhaust. I went with Speed Engineering headers just because no TBSS manifolds were coming up anywhere. I'll be getting back on mine soon as I have finally flipped my house. I could not fit the F-body AC in so I just recently went with a Holley Sanden style bracket and I am impressed with the stoutness.

[mtdave2]

https://youtu.be/mLys0vfCVr0

if anyone cares..lol. im done. glad i did it, the longhorn is now a bad mfer

[MySons68C20]

Beautiful job and very neat and tidy!!

[jjzepplin]

Looks very nice indeed! Sounds good too. Some more pics or videos are necessary though!

[mtdave2]

https://www.youtube.com/watch?v=Yj2TMHGOtQE

[bigmoe]

Glad you got it done! I watched the video hoping to see your documentation of the process but you skipped a lot, lol. Maybe you could go back to your original questions and provide your solutions. Might help some else doing a similar build.