It really depends on the car, size of the tank, and location. I really like Moon tanks, and I wanted one on my Austin, but I held mine up in every place I could think of and it looked like a wart sticking out. Just could not find anywhere that it looked good.
The old roadsters look great becaue they sit between the frame rails, and a lot of cars llike the Tri Fives and old Willys coupes have a grille that they can be set back into and not protrude too far. If they sit back into the car or the grille they really add to the old style gaser look.
But even back in the day there were not a huge number of gassers running a Moon tank. When I look through the old Gasser Wars book probably at most there's maybe 10% of the gassers pictured have a Moon tank, so not having one will put you in the majority with most old gassers.