well i would have to say that i would go for the xtra cab! i absolutely love the xtra cab, they have tons more room and look unique. they are alot less common than a standard cab. plus you were saying how you would preferrably have something with a little more room, so i would deffinately recommend it because of that. yes it does look like a skyscraper but that can be fixed easily.
comparing the two trucks and the accessories they have, i would still probly choose the black one. i would much rather have a detroit in just the rear than possibly having both diffs welded. you dont know how good it might be welded and you can never know when the welds might fail, and if they fail while cruising down the highway, its most likely going to take out your gears too. plus a lock right is only about 275.00 buy one and put it in the front and it will be way better than being welded.
so the silver one has duals which is good, but all you have to do is buy a low gear set and install it in the black truck then you will have about the same crawl ratio.
also you dont know the condition of the engine in the silver one, and the guy is flaky, and it has a tranny issue! (not to be confused as a sexual joke! lol)
so here is my final overview.... get the black one, take the body lift off, spend about 675.00 on a front locker and a low gear set for the case and you will end up with a truck that has the room you want, is built better than the silver one, looks nicer (less body damage, plus its an xtra cab so it just looks badass!) and has a brand new engine! i also dont like the fat boggers on the silver one. well idk if it helps at all but thats how i look at it! stick with the xtra cab for the room, you will be happy you did
