318 vs 340

Currently the car has an original 318 with factory AC; I have a '72 340 bare block with 2.02 heads. How many parts can I use from the 318 to build the 340?
I’ve been told that all I need to purchase are pistons, cam, 4 bbl intake, and exhaust manifolds. Everything else can be used, i.e. crank, rods.


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The 318 and 340 used the same length rods, same stroke and same journals sizes so fundamentally you can use the crank and rods. I'm not entirely sure if the 318 components are as strong as the original 340 parts or not. The early pre'72 340's used a steel crank not cast. I'm not sure if the 318 crank is forged or cast but depending on the HP level you're seeking it may not matter so long as it is crack-free.
The bigger question to answer is what sort of compression ratio you're trying to obtain. The early 340's came through with 10.5:1 compression which was created with pistons that protruded above the deck and were matched with open chamber heads. Trying to obtain something in the 9.5:1 range and maintain a .04 or so quench is a challenge with those open chamber heads.

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