What's it for? Not too knowledgeable, but I think early rbv's had low pressure in tank fuel pump feeding high pressure pump mounted on frame rail. This was to keep the high pressure from running dry or it was that the high pressure couldn't self prime. Perhaps if you research this you can figure a way to enlarge the stock openings. Otherwise by an aftermarket tank with the fittings you need. My research shows pricing from $~50.00 to above $1700.00.
Good luck and keep us posted
Richard
Good luck and keep us posted
Richard