I wasnt sure were to place this post , I have a question can you fit a 95 impala/caprice fuel tank in a 1970 caprice I know I'm going to customize the floor bored because of the hump to clear the pump assembly but would i be able to strap it down with the original mounting points or do I need to customize that as well
Haven't done it personally, but a buddy put a 94-96 tank in his 65 when he swapped in an LT1, so you should be able to get it to work. Don't think you need to clearance the trunk for the sender, either. Use the filler from the 70.
Modern gas tanks use a vapor dome on the top of the tank to keep the tank vented without allowing liquid fuel out (an anti-pollution thing). They are comparable in size so you should be able to adapt one to fit under your car but it will not be a bolt in.
Another option (though admittedly a much more expensive option) is to buy a custom made stainless steel gas tank designed to support EFI (non-vented with return line and high pressure fuel pump submerged in the sump of the baffled tank. Stainless is required because alcohol in the fuel makes it acidic and it causes galvanized or aluminized factory original tanks to soon begin to rust internally.
Thanks for the info there's a few of these tanks near me on craigslist for $50-100 with the pump there is also a guy at the the long beach and pomona car swapmeet makes any custom stainless steel tank of your choice for $400 flat but I'm on a budget lately