[tjakab]

I never tried AD&D to 4th edition, but to 5th edition you can pretty much just do it on the fly. 5e characters are more powerful than their 1e/2e counterparts, so you'll want to increase HD and damage for monsters or just swap in the equivalent from the 5e Monster Manual. You also won't get direct indicators for skill checks or DCs, but those are usually simple enough to figure out.