TOPIC: '60s Big Twin / Lark 40hp fuel pump not pumping

I've had to swap out the '66 cylinder/crankcase for one from a '63 due to crankshaft damage. Among several other things, the fuel pump on the '66 mounts directly to the upper bypass cover, so the cover was also swapped. Now the pump doesn't pump. The engine runs but drains the carb unless the primer bulb (which goes soft) is squeezed. Disconnecting the hose to the carb and cranking the engine, no fuel. I opened the pump to look for damage, none that I could see. I installed the newer style square pump and the same, no fuel. The fuel lines and bulb are all new. The pickup tube screen in the tank is clean, and the tube is intact, no leaks. There is a small hole in the bypass cover and air is pumped out of it when the engine is cranked with the pump removed. Any suggestions or ideas will be appreciated.

I replaced the fuel pump a second time using the 438556 pump for 20 hp and up instead of the 388685 which is for smaller engines which was suggested by marine engine.com The engine runs fine. I had to file a bit on the throttle linkage and the back edge of the pump to avoid some interference. Unless the 2 smaller pumps were defective, they were not working on the 40hp engine...