Rodtec1, The first starters that bolted up from the bottom that I saw on the early small block was on the ones coupled to the Turboglide trans which came out in 57.Powerglide and manual stayed with the same 3 bolt starter until the aluminum powerglide which arrived on 327's in 62 and the aluminum clutch housing same year had the starter bolted up to the engine.I think 409 still bolted the starter to the clutch housing thru 64.In 62 most 283's were still using the cast iron PG while 327 got the aluminum ones.
The key was as spectra said the ring gear size dictated where the starter bolted and most trucks with manual would have kept the 3 bolt starter and large flywheel but aluminum powerglide in truck would have had the small ring gear and starter bolted to the block.So when did the truck get the small flywheel/ring gear?
The 64 parts book says "57-61 all and corvette 8cyl except turboglide"--this would be the 3 bolt that bolts to conv/clutch housing.
"62-63 passenger & corvette w/PG (327)& 1963 series 10-20 w/PG and 292".This would have been the starter bolting up to the block. They offer one for turboglide only 57-61--no mention of the "terribleglide" for truck and it seems to have been superseded by the aluminum case PG in 62(why did it take so long?).

Bob Taylor