So I did this dance back in the '90s when I got my C60 bus.. dutifully rebuilt the rear brakes with all new hydraulics, shoes, and all four wheel bearings and seals, I even found a pair (the last pair) of 15x4" drums. Brakes great.. worn out banjo housing rear end for which parts didn't exist in 1993, not as great. Long story short, I wound up swapping in a later T170 axle and of course I had to buy all new shoes, springs, wheel cylinders, and seals (IIRC I got lucky on the bearings which were still OK, at least) once again.
If the rear end currently in the truck is good-as in doesn't leak, isn't noisy, the two speed still shifts, is somewhat decent in being able to go more than 55mph if you had to.. then go ahead and do its brakes. The trouble with the T150 is that one of the side bearing races *doesn't exist.* Like, I had to have one made back in the '90s and it was almost $500. Also nowadays, the only other available ratio, 5.83:1 ring and pinion doesn't exist either. Another exciting wrinkle in this story, is that back then the T170 was the modern option, you could get parts for it at the dealer. I've had this bus so long that the updated axle I installed is now deprecated, but at least it's just the ring and pinion that's scarce as chicken lips. You can still get the bearings for it.
I guess the moral of the story is, if you aren't gonna drive it a bunch, then what you have now will probably work and you can give it new brake shoes.. BONUS: those 15x4" brake drums also *do not exist* so the 13,000lb rated 3500HD axle swap keeps looking better and better.
