Not a big deal.
You need to pull the old pump, and buy a blockoff plate. The speed shop may not list one for a BB mopar. But the one they sell for a BB chevy fit's right on, so use it.
Then decide what pump you want, and get to mounting it.
If you are going with a performance pump, like a holley blue, it needs to be mounted lower than the fuel tank, as it is a pusher, not a puller, and you may need to have a sump put into the tank for it to work.
There are more generic electric pumps available, from Carter, that do pull the fuel better, and are quieter too. These are more forgiving in mounting location, and won't need tank mods.
It all depends on power level etc..
