The transmission you want won't hold 500 HP, the engine you have is making 250 horsepower, give or take..
You can't boost the compression and add a supercharger, it's actually best to have it a little low for a supercharger. You can probably get an engine to run 350 HP with another set of heads and you will have a ton of fun with it.
As far as the 5spd, what came in 1500's of that era was a NV-3500 which is a very weak/ finiky trans and has a rating of 300 ft/lbs. Any more than that and it starts to come apart ( and there are NO upgraded parts ) What you have is ither a super rare SM-265 that was basicly modified to fit the '88+ trucks ( only found in 3/4 ton and 1 tons for a couple years), a SM-265 for a '73-'87 truck mod'd to fit or an NV-4500, found in M/T 3/4 ton and 1 ton's after like 1992. It's 4 speed plus a granny gear, but is considered a 5 speed, shifts like a truck trans, can't shift it very quick, but it'll take a lot of power ( same trans as 5spd Cummins Dodges ). Your 5spd options are basicly transmissions that will cost far more than a grand to buy ( Tremec 3550 or TKO 500 would do well ).. The easiest thing to do is accept that it's not a race car, build the engine enough that you can have some fun while being practical..
What you want will cost $20k easy.