The suspension looks not to have changed much, if at all, since those early days. You can probably refit all the running gear without issue. Obtaining the gearboxes, however, is likely to be a problem (and expensive, in any event). It could be that the drive sprockets are slightly different. The existing rear track tensioner can be replaced with a Henntec unit, most likely. Alternate drive units could be fitted, as well as an alternate Controller system (MFU's are overpriced and not over here).
As Painless, suggests, it's worthwhile leafing through previous Tamiya KT rebuilds here.
Oddly enough, I rather like the neatly engineered 'analogue' clockwork look of Tamiya's early KT.
Enjoy the journey, whatever you opt for.

"Get your facts first, and then you can distort them as much as you please"- Mark Twain.