I've never done the upgrade to a later model Nippondenso ('89 later ). I would think you would at least need to change the inner primary and maybe the outer also. I usually go to a Spyke brand for the earlier type systems with excellent results.
Yeah, Blueglide. I had that problem when I was assembling my Johnny Casher.
It does have to do with the differance of the jackshafts. The diameters of the bushings were changed in the later set up in the primary cases. I had bought a '94-later starter and jackshaft but had pre '93 cases. I bought both set of bushings for the inner/outer primarys and with a little modifications adapted them to press into each other for the desired clearances. Actually the bushing for outer primary doesn't need to be used. It makes a perfect size 11.5 men's biker ring, complete w/ HD p/n on it. (Polishes up nice). Also the retainer bolt for the jackshaft changed from 1/4" pre-'93 to a #10 later. Watch your compatibilitys. Get yourself a vernier caliper. Indispensable.
What ever system you're using, don't scimp on the battery! Best bet is to have at least a 300cca, and you won't be disappointed. The starter HAS to have that first kick in to get things rolling.