Mechanical Fuel Pump Choice 340 stock Street Demon 625 Carb

Just about any old Mechanical pump will fuel that beast.
But Ima thinkin the stock 340 pump will be just fine.Even with the stock 5/16 line. I would replace all the rubber lines and the filter(use a metal can) and check the in-tank sock.Use as little rubber line as possible. Fabricate a metal line from the pump to the carb, if you have to. I put the metal filter on the suction side of the pump. It's harder to change, but I put a big one on there, back near the tank, and it's been on there since 1999.
For peace of mind or in readiness for future upgrades; the Carter M6902, hi-volume pump is very good. I have had this one on my 360, since 1999 as well, with a 750DP, and it goes to the big end,easy. No regulator,no return. A 3/8 line is recommended for extended high-rpm operation;All the way into the tank