I suspect that any handy carpenter would be able to retrofit bunks pretty easily into an existing 42T (American Coach offered it as an Allegiance 42T in 2009 to 2010 and then Revo in 2011 to now - I think the Allegiance might actually be a bit higher trim than the AC Revo). One thing I'd look for in an existing one would be a booth (although again, a carpenter could retrofit one)
For pics, here's a link to Allen Crabtree's converted 42T (I hope he doesn't mind):
http://s882.photobucket.com/user/allencrabtree/library/?sort=3&page=1I believe American Coach have pictures of the same unit on their FB page
https://www.facebook.com/media/set/?set=a.245061165530938.53376.178025815567807&type=3In that one, the W/D was swapped out for a combo unit and it was pivoted to open into the bathroom but that's probably not really necessary although it might be nice if you want to use it while the kids are asleep. I do like how they have the ladder that pivots although I'm not sure how useful it would actually be (it's a bit hard to tell from the pictures; maybe there's not that much room to access the lower bunk when the ladder is in place and with the tall cabinet so maybe it does serve a purpose (looking at the pictures on the photobucket link, it looks like it might be a pretty tight fit with the ladder 'in-use'). They also replaced the half height dresser with a taller one and they added cabinets on top of the combo W/D and at the head of the top bunk.
If you get pics from AC, please post them as I'd be curious to see what they propose.