Welcome to the forums! I concur to getting a factory TSM for your year, it will help a lot.
I have done a few conversions to and from propane, granted none of them were on jeeps, but all carb engines are very similar. Most were strait forward from LPG back to gas... Just remove the propane tank (after its emptied of course) and the lines/fittings/ect. The motor side was just as simple as replacing the LPG carb with a gas carb, installing either the mechanical fuel pump on the block or an electric pump, installing a factory tank with sender/pickup in the stock location and running 2 fuel lines and 1 wire for the sender. That was on '77 ford f100... A bit more complicated going from gas to LPG...
An ECM controlled motor, well thats a different story... quite complicated...
1974 Jeep J20, gladiator grill, 12v p7100 cummins, Modified He351, 4" strait piped, NV4500/Ford NP205, 14b front kingpins, 14b rear, 4.56's, 12" lift, 37x12.50x16.5's