Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
Hello and welcome to our site. My name is Steve.
Sorry to hear you are having issues with your truck especially when it comes to changing the engine.
The 1979 engine will not work with your 1994 Silverado without serious modifications. In 1988 GM redesigned the block,cylinder head, intake manifold and exhaust manifolds. The 1979 block is not drilled for mounting the accessory brackets that are needed in your application. The engine block mounting pattern was slightly changed by a 1/4 inch for the new design of the vehicle frames. The 1979 block is not drilled for the knock sensor as well.
The list goes on and on when it comes to making things work. I'm not saying that you can't make this happen and I don't know if you are the type of person that can modify things but this would be a major and expensive project to make this work out for you since everything was redesigned.