bear said:
thanks for the info, just to clairify, I should make the return as big as the feed line? Also where should I have the return put? The tank has a "tit" on the passengerside rear. There is a hole in the floor of the car at that same spot if I am not mistaken.
Yes.
The only problem with using one of the existing vent nipples on a gas tank other than the '75 tank (designed for FI and won't fit GT) is that you will have noise (splashing sound) from the returning gas. Since the vents are at the top of the tank, the more empty the tank, the louder (echo) the noise is.
A word of warning about the '73 GT tank: Under NO circumstance use the tank's "vapor return" nipple (smaller line from the fuel filter back to tank on the '73 models only) for reason already explained!
A lot of people make up a new "T" for the filler neck hose with the nipple welded in it. Sound will be isolated from tank because it does not directly "splash" into it.