I'd drill about 8 holes, 4 in the corners, one in the middle of each edge, then get foam tape and some j-nuts and bolts. That's how the volvo sedans are.
That makes sense. I guess with my 84 it's really not that big of a deal since the fuel pump is on the engine, the only thing in the tank is the sending unit which sort of works, as best as I've ever seen them in these older trucks. Sometimes my gauge is right, other times its about 1/8 off.
The access plate though is a definite help regardless of which year B2 you have. If I had the access plate I'd definitely get in there and look into the cause of the fuel gauge fluctuation sometimes, just lots of work to drop a full fuel tank.