As far as I know, the senders that are drop in compatible with the vr4 fuel tank had the box style low fuel warning sender.
It did come in two styles of pump hook-up
{
click on pic for a detailed look)
One that used a flared / bell bottom and an o-ring to seal a factory style pump, and an electrical connector that slid onto the connections at the pump
And there is also one that used a hose (perfect for modding / adding a big pump).
It hooks up electrically with eyelets and nuts at the top of the pump.
I believe the hose style is from the ggsx, anyone know for sure?
edit; found some pics with the part numbers /ubbthreads/images/graemlins/smile.gif
hose style (ggsx?)
Bell mouth style (vr4)