Not sure where to post so here goes. Wanting to Shorten a longbed single cab to a shortbed. Need gas tank help.

[mofoco12]

Sorry and admin move to appropriate forum if need be. I recently bought an 83 single cab longbed diesel. Been using it as a daily and it is a keeper. Bed is trashed and I like a shortbed better. Already got a pristine shortbed. I know how to shorten a frame so no issue there. Require a definite on whether a singlecab shortbed tank is what is needed for the conversion? The tank on it now is way too long. So is there as part number I should be looking for? Thanks.