350 to V6 Swap Tranmission Location

[1972RedNeck]

Have been collecting parts for my 350 to large V6 swap (stroked 478M) in my '72 K20. Have a complete 305 out of a '67 K2500 with bellhousing, cross member, etc.

The question I have is a minor one.

Is the transmission mounting location in a 4X4 the same for a small block Chevy and a GMC V6? I.E., when I bolt my V6 to my SM465 and NP205, will I have to slide the whole nine yards forward to gain firewall clearance to make it fit? Will the GMC bellhousing even bolt to the SM465? (I assume it had an SM420 bolted to it, but it very well could have been a NP435 as well)

[Bob B.]

I don't know anyone who has done this swap, but the stock location of the V-6 is very close to the firewall. So close in fact it is difficult to remove the right valve cover unless you turn the engine over until the #6 exhaust valve opens! My guess is it is about where a small block would set. As for your '67 bell housing, it should be for the SM420. The NP435 was in 4X2 trucks only, at the time there was no transfer case adapter that would bolt to it. Dodge used a NP435 in their 4X4's those years, but with a divorced transfer case. Now, about mating an SM465 to an SM420 bell housing, it can be done. Read this:

http://www.novak-adapt.com/knowledge...s/manual/sm420

https://www.novak-adapt.com/knowledg.../manual/sm465/

Installing any of the large GMC V-6's, specifically those with gear drive cams, presents a few other issues. The timing cover is much larger than those V-6's with chain drive cams, and some parts mount differently. You might try asking here, some of these guys have done that swap:

https://6066gmcclub.com/forumdisplay.php?f=4

[1972RedNeck]

Originally Posted by Bob B.

I don't know anyone who has done this swap, but the stock location of the V-6 is very close to the firewall. So close in fact it is difficult to remove the right valve cover unless you turn the engine over until the #6 exhaust valve opens! My guess is it is about where a small block would set. As for your '67 bell housing, it should be for the SM420. The NP435 was in 4X2 trucks only, at the time there was no transfer case adapter that would bolt to it. Dodge used a NP435 in their 4X4's those years, but with a divorced transfer case. Now, about mating an SM465 to an SM420 bell housing, it can be done. Read this:

http://www.novak-adapt.com/knowledge...s/manual/sm420

https://www.novak-adapt.com/knowledg.../manual/sm465/

Installing any of the large GMC V-6's, specifically those with gear drive cams, presents a few other issues. The timing cover is much larger than those V-6's with chain drive cams, and some parts mount differently. You might try asking here, some of these guys have done that swap:

https://6066gmcclub.com/forumdisplay.php?f=4

What about the '68 and '69 4X4's, would they still have been the SM420 or did they get the SM465? IIRC, the bolt patterns for the SM420 and SM465 are the same but they just have a different input shaft retainer diameter...

[MusicMan70]

Checkout ERL's 68 thread; May wish to PM him for more specifics.

http://67-72chevytrucks.com/vboard/s...d.php?t=635053

[palallin]

My '69 has the SM465.

[Bob B.]

The SM465 replaced the SM420 in '68.

[1972RedNeck]

Originally Posted by Bob B.

The SM465 replaced the SM420 in '68.

So a 68 GMC K2500 with a 351E would have an SM465 and NP205?

[BobS]

'68 still has the Rockwell, first year for the NP205 was 1970 so no V6s came with the 205.

Bob

[BobS]

....but the '68 would have the SM465. Sorry, missed that first time around.

Bob

[Bob B.]

Yes and yes to what BobS said. The '68 V-6/SM465 bellhousing must have been a one-year only part in pickups, though I suspect it was probably in medium duty trucks up to 1974.

[BobS]

I was just reading your original post. I have a 67 K1500 that went from a V6 to SBC. It doesn't look like they moved the transmission/transfer case in the swap but I haven't pulled everything apart yet to make sure. I bought the truck to use as a template to convert my 70 K20 to a V6 truck since the original clutch bellcrank pivot bracket is still on the frame. I should finally get the project underway this spring, everything is covered with snow right now but I could try to get some pictures if it would help.

Bob