Looks like some items from the 273 ended up on the 318. Did the solid cam adjustable rockers and push rods? If so, I'd reuse them and keep/make it a solid cam engine and use a cam similar to the 273 4bbl specs. Opening up the heads for bigger valves can be more expensive than buying new aftermarket aluminum heads. If you have that kind of budget, I go aluminum so you can bump up the compression ratio and still run pump gas. If it were me and keeping the costs down, I'd just clean up those head with a nice 3 angle valve job and maybe some minor porting. Using the stock exhaust manifolds would kill most of the flow advantage of the big valves anyway. I'd rebuild the 625 carb and use it. I'd also keep an eye out for a stronger rear axle assembly.....eventually you will need it! Oh, and one more thing.....a question about how they mated the crank to the converter. The original 273 would have had a small register in the end of the crank for the small button converter. A 318 would have had a large register. Did they put a reducer bushing in the end of the crank? Make a custom converter? Now's the time to address that too.
