There are numerous different versions of the "old" Mopar gear-reduction starter. They are
not all the same.
All the gear-reduction starters were electrically identical from '62 through early '73 (p/ns 2095 150, 2875 560, 3656 650) whether they went on a 225 or a 440 or anything in between, except all '63 engines and '64-'69 170 slant-6s got a starter with 4 series coils instead of 3 series/1 shunt. The 4-series starter (p/n 2098 500) has about 20% faster cranking speed than the 3-series/1-shunt unit. Rated power of both units is 1.3hp, though the 4-series unit is probably closer to 1.4hp.
In late '73 all engines got a 1.5hp version of this starter with 4 larger-than-'63 series coils (p/n 3656 575, 3755 900, 4091 975 and a few others). Cranking speed went up again.
All of the above starters have 3.75:1 gear reduction.
In '74 the large-frame 1.8hp version of the starter, with 2:1 gear reduction and
much higher cranking speed, was released on 360, 400, and 440 engines (p/n 3755 250, 4091 950, and a few others). From '74 through '87, the small-frame and large-frame starters were electrically unchanged and were used on various engine sizes depending on year, assembly plant, emissions package, and phase of the moon.
All the above starters interchangeable as long as you've got the space for the ~½" longer large-frame starter compared to the small-frame unit. Only a few of us
really geek out on the differences among them.
The first version of the Nippondenso-made mini starter was used on Mopars in late '88. Subsequent versions of it were made smaller and more powerful. Yes, the mini starter
is more powerful than the Chrysler-built unit. That is why it spins the engine faster. It is a very well-designed starter, and as long as you get the real Nippondenso (later "Denso") unit and not the Chinese copycat junk, it is a very well-built and durable starter. Its only drawback is that your old Mopar will no longer sound like an old Mopar when you are cranking it.
It is difficult but not impossible to imagine a situation wherein the mini starter won't fit. Usually the difficulty is with placement of electrical terminals (i.e., they hit stuff). See
here for adaptation info.
(note that '60-'61 worldwide slant-6s, '63-'66 Canadian slant-6s, some '70-'71 US slant-6s in passenger cars and a good number of slant-6s in trucks, as well as certain 426/4-speed rigs, got a direct-drive starter that does not interchange with the gear-reduction unit because the drive pinion on the DD starter has 9 teeth and 25mm diameter, while the drive pinion on the GR starter has 10 teeth and 33mm diameter).
Any more questions about starters?
