Rob-

2 quick things.
Do you know anybody who has cut the holes in the floor and what diameter and have r+r there fuel pumps through that hole??
I see that option talked about, and good in theory, I never heard how well it worked out in real life. I keep thinking you need a really big hole to manouver the fuel pump in and out of the tank, as well as getting the lock rings twisted and in place square and proper. Not saying it cant be done, but when I have looked at accessing the fuel senders 2-3 " below the floor, i wonder how big of a hole is needed to service?

2nd item is when I have had fuel tanks down it is more then obvious where to drill up. The last coach I did, i hole sawed out the foam, and drilled up into carpet with a 1/4" bit. You wont need to lift the tank to mark anything from bottom.

If you look at my photos you will see the factory already has a hole for senders. At least on my 75 and the 77 i did tanks on.