Wheel studs are pretty universal, they can be used in many different vehicles. You don't have to have the exact stud that originally came on your truck, you just need to have one that is reasonably close and the drum can be adapted to allow it to work.

Get the old ones out and make some measurements. You need to know the over all length of the stud, the thread size and count, the shank length, diameter, and the length of the serrated teeth. Without measurements, you are searching for an unknown stud out of 100s of possibilities. Remove a stud and get some measurements.

Then you locate an auto parts store that has a Dorman book and knows how to read it. (if you get measurements, someone here can help you with this.) You find a stud, among the 100s listed that comes closest to your measurements. Important numbers are thread size and thread count, with a shank diameter the same or slightly larger then what you have, and the serrated teeth length can't be longer then your old studs. Buy new lug nuts for the new studs.

Then, if need be, you drill or ream out the stud holes in the drum and hub so the new studs will have the proper interference when they are pressed in.

There are 2 reasons you are having difficulty.
1) Very little info concerning part numbers on component parts (like wheel studs in a drum and hub assembly) exist. You would really need to have a parts book on hand covering the very specific assembly you have, and then, wheel studs were often a "this one or that one, what does yours look like?"

2) Regardless of what your title says, or what the numbers on the truck say, except for the mid 70s vans, all normal Mopar 3/4 ton wheels were either 6 lug, or 8 lug. They normally didn't make a 5 lug 3/4 ton truck wheels, all trucks with 5 lugs were 1/2 ton. Now there may have been a dealer someplace that sold a 1/2 ton pickup they had in stock, as a 3/4 ton truck, in order to move it off the lot. Lots of stuff could have happened over the years, including axle swaps, or hub changes. Your having trouble finding 3/4 ton 5 lug hub parts simply because that configuration was out of the normal. Everything on your truck might well be a legitimate 3/4 ton truck, but the parts I see are not of the normal. If you seek parts from an abnormal truck, you can't expect to find them looking at the normal stuff. Expand your search for 1/2 ton stuff. Gene