For this, first thing for a recording will be to double track the guitars. NOT copy, but actually double the parts. This will immediately open up the sound. James is actually an excellent player and his rhythms are amazingly tight. However, the tracking will be one piece of the puzzle.
The original recording was done in '82-'83 and they weren't HUGE and produced back then. It could easily be just the guitars tracked, maybe even more than twice. If you listen with headphones, you can hear the 2 guitars.
They may have added effects after the tracking was done... but not during. The slight difference in the 2 guitars is what causes the sound you're hearing, not reverb (but what do I know, I can't hear much anymore).
If you want to try out some effects, go for it. Mix them in slowly so they don't overpower the sound. Obviously there are some songs that have distinctive effects, however Seek and Destroy is the best example.
Good Luck