The only problem you might run into with the AW4 is what transfer-case to use, you cant use the NP242 or the NP231 because the front drive-shaft drop is on the driver side unlike yours which is passenger side. I think if you use a post-93 AW-4 you can mate it up to the Dana-300, but don't take my word on that I can't fully remember. Aside from that it's an excellent transmission and will hold up just fine behind the 258. Best of luck to you on whatever you use.
1968 J2000 Gladiator : AMC 304, AX15 5 speed, Dana 300, Dana 44/44 4.27 Gears (W.I.P.)
1969 Triumph GT6+ : 6cyl, 4speed, resto in order, (on the back burner)
2015 Ram 2500 CCLB 6cyl Cummins, Stock