That works, it can be a 1969 thru 1980 302, 327 or 350
3970010....302.....69....4...Z-28 Camaro
3970010....327.....69....2...Trucks and industrial
3970010....350...69-80...2 or 4
This bugs me so I keep looking. Found the GM350 used by Merc for inboards from 1969 to 1972. The fuel pump used was 47822 and actually found one at Outboard Paradise for 99. Not saying this was your pump but it does not cross to others and its just two years away from yours.
Are you sure that the pick up tube going into the tank is clear. I once had a customer's boat that did some weird things. In desperation we took the boat out with a 6 gallon out board tank and ran the boat until it started nosing over. Hooked up the O B tank and it ran good. Turned out there was a small filter in the pick up tube that had what looked like fuzz and I could blow through the tube with no resistance but when I hit it with compressed air it shot out on the floor.