Having TR and NA and NC Miata experience, you will never get a TR series car to behave like a Miata. There's just too much flex in the TR and the greatest of 50s and 60s LBC technology will keep it from acting like a modern car..
If you are looking for performance, then perhaps polyurethane, Delrin or Nylatron would be even better on the bushings, but it doesn't really sound like that is the route you want to reading through the thread. So if you are looking for comfort, or at least what passes for comfort in a TR6, stick with the stock rubber bushings and differential mounts. The one possible exception would be the upper front bushings which could benefit from something harder from a service life perspective. I would highly recommend replacing the trailing arm brackets with the adjustable trailing arm brackets from Richard Good (
> Adjustable Trailing Arm Brackets | Good Parts < ). They make life much easier when it comes time to dialing in rear ride height (depending on springs a spacer may be needed as well) and rear camber. The standard way of setting rear camber is playing mix and match of one, two and three notch brackets with notches oriented up or down, a royal pain that is somewhat removed from the neck. If you have ever been through that exercise, you will probably think it is money well spent. I know I did and others that have bought them that I know felt the same way.
Springs, definitely try to figure out which springs you have, if you have uprated springs, you may want to replace them with standard springs from a comfort standpoint. Part of the problem with the uprated springs is that it is hard to get good information as far as spring rate and spring length go, they generally talk in terms of "xx' % stiffer than stock, but that doesn't provide what you really need to know. Again, Richard good does a nice job of giving spring rates OD, ID and length but here all he offers are performance oriented springs. Dampers are another consideration. If you go adjustable up front along the lines of Spax or Koni, I would advise setting them about one third off full soft initially, bearing in mind you may want to adjust the damping a bit up or down depending on which springs you use. On the rear, you can get Armstrong stuff from the usual suspects or the rebuilt units from Apple Hydraulics, I have had good experiences with stuff from Apple (
> ONE PAIR - Triumph TR4A, TR250, TR6 Rear Armstrong Lever Shock Absorber < ).
Other than adjustable trailing arm brackets and possibly those upper front arm bushings, the one thing I would suggest as an upgrade would be a good set of anti-roll bars. They will do the most to control body roll without going to stiff springs and generally have little cost from a comfort standpoint. I have had the ADDCO bars and while they are priced lower, I thought that the set up for the end links was rather screwy and neither bar is adjustable. I would pony up the extra dollars and get the bars from Richard Good, the rear bar is adjustable so you do some tweaking with roll rate contribution from the rear bar to your preference in the handling department (
> Anti Sway Bar Kits | Good Parts < ). I also think that Revington TR out of the UK has a front bar that would pair well with Richard's rear bar. The reason I don't think in terms of recommending Revington's rear bar set up is that it is designed to work in conjunction with their rear damper conversion kit and that in turn requires welding some reinforcing bits to the frame along with an upper damper mount plate and a modifications to the trailing arms to run tube dampers up the middle of the spring. A very nice set up, but outside the bounds of where many TR6 owners would want to go. See attached pictures for example.
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