How old is your tank ?..... Run out to it and take a picture of the ASME nameplate with your cellphone ... then post it here, on this forum
I strongly suggest that you reconfigure your existing LPG pump suction piping to enable you to draw from an existing nozzle.
LPG BULLET tanks are typically very old, marginal containers of dubious pedigree ..... These were a "market commodity" sold and traded much like baseball cards.
I assume that you are adding a new nozzle to the tank bottom
MJCronin
Sr. Process Engineer