fuel gauge wire question

[WAAF]

So, like so many others I moved tank to under thy bed..
now my junkyard extra behind seat tank I took the fuel sender wire. with a elbowed plug that is a slip on fit. it pushes on the sender screw on the tank to send the info to the fuse panel then gauge.. now that the tank is outside and in the weather.. is the push on plug enough.. or would/should A o ring connector and nut be a better bet.. as it'll royally suck to have to drop tank/remove bed if this push on plug looses connection from the bolt it slips over rusting/etc..
also does anyone know of hand what thread size this stud for the gauge on the sender is? it be nice if it's the same as a starter that way I can use a brass nut..
thanks for anyhelp..