A completely stock Ford in-tank electric fuel pump from a mid-'80s Ford TBI system will attach to the late Pantera fuel sender system and will pass thru the stock tank hole without alteration. The tank can stay in the car if you work thru a removed left rear quarter window. The sender system out-pipe must be shortened and leakproof wires added to power the new pump. All this has no effect on the fuel gauge. The well tested stock Ford pump is very quiet in operation. All this was the subject of an old illustrated POCA Newsletter article.
TBIs run at 12-14 psi so an external regulator is usually needed to cut pressure to 5-7 psi for a carb. Significantly, a Ford EFI pump looks EXACTLY like a TBI pump but delivers 45-55 psi and CANNOT be regulated down to 5 psi without overheating. Once out of the box, one cannot tell the pumps apart. If you're running EFI, be sure which pump you have. If you have an early tank, the welded fuel-out boss can be used for an EFI fuel return, even if its rust-perforated inside.