Your ^^^post here^^^ is spot-on. The majority of Class C's you'll find in your year (read that price) range will be on Ford. The early ones with 460 then 1997 and later with V10.
I believe the following to be true:
460 went EFI (throttle body/TBI, not the newwer more sophisticated MPI (multiple port) starting 1989. I believe (haven't dug into this) they stayed with the C6 transmission (three speed automatic, no overdrive) through 1991
Then, 1992... Body style changed from the angular 1975-91 look to the rounded 1992-2007 look. I do not know if they changed the EFI to MPI right away or not. What they DID do is go to E4OD (four speed overdrive automatic) which is an improvement. By 1996, the 460 was pretty slick. MPI, serpentine belts, totally modern.
Time out. I'm talking CHASSIS years. RV's are sold and usually titled by the manufacturer's designated model year and often the chassis is prior year. In some years, that's important. Example, you go look at a "1992" Class C and find the old angluar chassis (1991) with TBI and the C6. The next "1992" you look at is rounded, has overdrive, might be MPI. Other years are not that critical. Our "2003" is on a 2002 chassis and I wouldn't really care if it was on 2001, 2002 or 2003 since those years were very similar.
1997-1999 was first of the V10's with 275-HP and about the same performance as the last of the 460's. Some of those engines had problems with spark plug threads. At least some of that trouble seems to have been from improper mechanics. E4OD was modified all so slightly and named 4R100.
2000 and later V10's went to 305-HP with "Performance Improved" heads that also addressed the spark plug issue.
All Class C V10's are "two valve" engines and their top HP is 305. Some will talk about 362-HP, "three valve" engines. These are F-Series (pickups and Class A's) ONLY. This also relates to why a diesel class C is no big deal. They are NOT all spun up like the ones in pickups. Space and heat dissipation conditions dictate this. Very mediocre driving experience.
Chances are the true Class C's you find will be wide-bodied, about 101" across the house body. There ARE downsized C's often referred to as B+ and those are narrower, lower, and usually shorter than true C's which have a big cabover overhang, usually with bunks but sometimes entertainment center. B+ has only an aerodynamic fairing between chassis cab and fron to house body.