I had a 59 short bus that I let go to a new owner last year. I considered the same thing you are before letting it go, because I knew I would not get around to doing them.
However, I believe the more efficient path is to address the issues on your bus. As you probably know, you can do a rear end swap (P30?) for disc brakes and convert the front to disc as well. Attaching an automatic transmission behind the 350 should not be tough and must be a way to do power steering etc.
Anyway, just my opinion and I believe it is a project worth doing and wish I had more time to do the one I had.
Good luck on your build. You will get great advice here!
~ Victor
1941 3/4-Ton Pickup (in process). Read about it
in the DITY Gallery1955 Grumman Kurbside "Doughboy" 235/3 on tree w/ OD
1957 3100 - moved on
1959 C4500 Short Bus "Magic Bus" - moved on
1959 G3800 1 Ton Dually "Chief" - moved on
1958 C4400 Viking "Thor" ~
moved on to fellow Bolter