Just my opinion, but making a 60 cubic inch change in engine size will make it run way too lean. I swapped a carb intended for a 292 Ford onto a 239 flathead once, and it had a horrendous flat spot just off idle unless I was very careful with the throttle opening. The bigger venturi drops the air velocity and internal vacuum in the carburetor bore enough that it has trouble flowing any fuel at all into the airstream. Bigger jets help a little, but not much because the venturi vacuum just goes away at low to medium RPM.
Jerry
