I have an 84 Z28 and just finished taking out my 305 and dropping a 350 in it that came out of a 91 cadillac. It doesnt have a place for a pushrod to install a mechanical fuel pump so i mounted an electrical fuel pump close to the tank. Now the engine runs hot and i think its because it might be running lean on fuel because after driving for a while it barely pumps fuel. Does this sound like the problem? If it is, how can I fix it, and if it isnt, what else could the problem be? Any help at all would be greatly appreciated.

Buy a better fuel pump and put a regulator on it and run 5-7lbs of fuel pressure...and check you coolant make sure you dont have an air pocket!!

If my heat riser valve stays shut, could that cause the engine to overheat?

if my heat riser valve stays shut, could that cause the engine to overheat?bypass that