Need to know a 383 w/TH350 in a 1964 GMC truck longbed?

[Kru]

I just bought a 1964 GMC Long bed with a inline 6 it needs some work on the motor. So how hard would it be to put in a 383 with a TH350 tranny? Also would it be worth it or not? Any comments are welcomed.
Mark

[siggyfreud]

You'd need new motor mounts, but it's likely the transmission mount and driveshaft could be reused depending on what transmission is in there already.

The better question is what are your goals for the truck? Power, MPG, cruiseability, weekend warrior, etc? What do you want to do with it. That should drive what motor/trans combo you pick.

[TheGreen61]

New motor mounts and trans mount, and most likely have to lengthen the driveshaft.

I had a 305 v6 and 3 speed in my 61 gmc (little different as the frame is different than yours) but when I did my 383 and th400 I used a aftermarket tubular motor mount from a later gen truck and found a factory auto trans crossmember. Had to get my driveshaft reworked with a slip yoke and a different yoke for the tranny.

[gabbin]

I think it would be worth the swap, depending on if you were worried about originality or not

[Captainfab]

If the I6 is a 230 or 250, you don't have to change the engine mount brackets. Just bolt new engine mounts to the small block and drop it down onto the frame brackets. As for the TH350, you will have to remove the bellhousing crossmember and install a trans mount crossmember. A trans crossmember from a '63-'87 truck will work.

[Kru]

Thanks for the input on this. I'm still torn on what I want to do with this. I would like to keep it original as possible but I also want to be able to jump in it and go anywhere and not worry about it taking forever because I can only do about 50. I would like to be able to get it up to about 80 if needed and not worry about it. But for the most part it will be a work truck. around the Pensacola area. But this is defiantly something to think about. Thanks to you all

[jtrichard]

Just going to a V8 and a automatic trans (for the most part) will NOT gain you any higher speed ( with converter slip you might even lose top speed) .....You will need an Over-Drive trans OR change the rear end gears

[Captainfab]

Installing an OD trans behind the I6 or changing the differential gears as well as taller rear tires will help reduce your highway rpm's. What rpm's is your engine turning at 50mph?