Well, I just thought I'd post some of things that I had to deal with installing a Vortec 400 into a 69 GMC pickup. Figured the information might save someone a few part searches with this information.
Where to start. The intake manifold. There were a couple things that had to be changed because the intake manifold only has 8 bolts and are angled different than the old intake manifolds. The original equipment carburetor uses a spring type choke. There is not a place on the Edelbrock 2116 (Vortec heads to Quadrajet carburetor) intake manifold to use this type of Quardajet and choke. Solution was to get a 1975 GMC Quadrajet and convert the metal heat tube type choke to an electric choke. Then onto the throttle. The 69 GMC uses a bell crank and rod type throttle assembly. I retained the bell crank and rod throttle assembly but had to remove the throttle cable stud from the 75 GMC carburetor. I also had to use a bushing, (1/4" inside to 5/16" outside) on the original equipment throttle rod to fit where the hole left where the throttle cable stud was removed (the bushing was only 52 cents). Next was the turbo 350 transmission kick down. I ended up using a kick down cable from a 75 GMC turbo 350 and a Holley 20-100 (check this website for a picture of the Holley 20-100 bracket http://www.holley.com/HiOctn/ProdLin...A/f20-100.html
) kick down cable/ throttle cable bracket. The reason for the Holley 20-100 bracket is that the Holley bracket will bolt to the carburetor, not using any of the intake manifold bolts. The Holley bracket would also allow the use of the more common throttle cable that newer Chevy V8's use. The Holley bracket has a place for the throttle return spring.
So that got the throttle, choke, and transmission kick down problems solved.
Next up to solve was the temperature sending unit for the factory gauge in the dash panel. The older heads are drilled and tapped for 1/2" NPT. The Vortec heads are drilled and tapped for 3/8" NPT. I moved the temperture sending unit from the head to the thermostat housing. The 80 and newer Chevy V8's have thermal vacuum switches mounted into the thermostat housing and use 1/2" NPT and / or 3/8" NPT threads.
I also upgraded the 69 GMC to a HEI distributor and and 64 amp internal voltage regulator 10Si alternator. It's not my truck, just doing business.