55.2-59 Where to put Chevy rad support on GMC frame

[Phungki]

So I have my 56 GMC frame and suspension pretty much rebuilt. I actually have more done than the pic shows. Kingpins are replaced and converted to disk on front. Sometime during its life someone replaced in front on the cab with Chevy parts. Heard this is common. I haven’t been able to find GMC radiator support or the other non Chevy parts. Oh well it is what it is. The issue I’m having is most of the parts regarding the radiator were in the bed when I got it. I have a factory assembly book for Chevy trucks and it shows where to put the radiator support on a Chevy frame but GMC does not have that bracket on the frame. I need so help determining where it goes on my frame. I found my donor sbc engine and transmission. I thought I would need to know where the radiator goes so I could figure out where to mount the engine. Is that right? And help would be appreciated. Advice, measurements or whatever.
Thank you
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[Phungki]

So I found a set of rad support brackets that mount to the frame. I guess I will have to put the cab back on and bolt on the inner fenders to find out where the rad support brackets go. Bolt those on, install the rad support and radiator and figure out where the engine goes from there. If that doesn't sound right pls let me know

[paulspickupparts]

Because you are mixing Chevrolet and GMC you have kind of created a customized truck. Mount your engine where you want with adequate firewall clearance Then decide where you want your radiator support. There were two locations for the support on Chevrolet trucks. 6 cylinder forward and V-8 farther back. Pretty much guarantee you bought the 6 cylinder mounts which will not give you the right height for the support. . You could cut them down. There is a filler plate top and bottom that was used for the 55-57 Chevy pickups with a V-8. They appear on ebay from time to time but are $$$ . Cheapest way is to do it your way. You will need a fan shroud at some point.

[Phungki]

Originally Posted by paulspickupparts

Because you are mixing Chevrolet and GMC you have kind of created a customized truck. Mount your engine where you want with adequate firewall clearance Then decide where you want your radiator support. There were two locations for the support on Chevrolet trucks. 6 cylinder forward and V-8 farther back. Pretty much guarantee you bought the 6 cylinder mounts which will not give you the right height for the support. . You could cut them down. There is a filler plate top and bottom that was used for the 55-57 Chevy pickups with a V-8. They appear on ebay from time to time but are $$$ . Cheapest way is to do it your way. You will need a fan shroud at some point.

All I have is a picture of the part I ordered. I do not know what engine it was for.

[paulspickupparts]

As someone else said . I would mount your cab and then the fenders with inner fenders to the cab Then attach your front clip. Do not install the radiator support mounts that you purchased. I would then put the correct hardware shown the photo to gauge the height the support needs to . Temorarily use blocks of wood of different thicknesses until you get the height you want. Then measure the height of the support mounts to see if they will work. On original Chevy pickups the V-8 mounts were not as tall as the 6 cylinder mounts. Also make sure you install the radiator support in the rear ward V-8 Support Holes on the inner fenders . If you mount it in the front holes the support will be too far away from engine fan .

Here is a pic of a V-8 setup from Jim Carter

https://oldchevytrucks.com/blog/inde...diator-shroud/

I can check , I think I might have the upper filler pan and possibly a lower.

[duramax55]

i would mount cab then motor then fenders and the figure out your rad location and support.. plan on putting it together a few times, 3 to 4 times before final assembly. i am on the third time to check every thing before paint.

[Phungki]

Originally Posted by duramax55

i would mount cab then motor then fenders and the figure out your rad location and support.. plan on putting it together a few times, 3 to 4 times before final assembly. i am on the third time to check every thing before paint.

Doesn’t the rad support connect to the inner fenders in a specific spot? I guess that’s what is confusing me. If these trucks did come with small blocks in them why wouldn’t I work back from the rads original position?
Granted I’m trying to use logic in an area I lack experience lol.