If you've seen some of my other posts, I'm sort of an anomaly since my truck is post-1973, but I was adamant about rebuilding it to stock and keeping the 250 inline six with the 3 speed Saginaw trans.
Regaring your scenario, I've pored through beaucoup truck catalogs for '73-'87 GMC and Chevys, and I would tell you that you should have NO trouble finding a 454 engine, they were available every year for that 15 year stretch and there must be a million or two out there in boneyards. Suburbans seemed to have a lot of 'em. Look for the letters Z ('73-'75) S for 1976-'79, and W for 1980-'87 in the VIN code--4th letter for '73-'80 and the 8th character from 1981-'87 will tell you that it is a 454 V-8. In '87 VIN code N designates a 454 with fuel injection, only year that option was available.
I haven't seen a 454 with a manual transmission, but I am sure there were quite a few made because there was a 4 speed transmission available each of those years. I know the 3 speed was standard from 1973 until at least 1984, which was the last year for the 250. There were 4x4s with 3 speed manuals from '73-'77, so there is a good possibility that some of those were 454 V-8s.
