Well, I know that the 555 was nicknamed the "triple nickle".
The 903 V8, well, from what I've heard, it produced about 300 HP- basically the same as the old NTC 290/300's. Some say it's worthless, but it was run by lots of freight companies. Fuel economy is suppose to be worse then the inline engines.
I saw a V 903 in a 1976 IH Transtar that had a 13 speed. I would guess that the transmission setup you are talking about would allow the engine to stay in the 'sweet' spot. This perticular engine was a natural aspirated, no turbo. A VT would be a turbo-ed version of this engine.
What do you plan on doing w/ this truck? When you say learn on, most 'modern' Class 8 trucks have 10, 13, 15, 18 speed trannies. Most, if not all, do not have the 'brownie box' anymore. In my humble opinion, depending on your funds, find a truck with an inline six and a ten or nine speed tranny. If you plan to use it for hauling (business), from what I hear, most companies that will insure your truck for long haul require a certain age range (unless it's refer trailers I'm thinking of).
