IMO the ride will depend greatly on which tires you use. Soft bushings may help with harsh riding tires, but I didn't notice any increase in harshness with the very hard Nylatron bushings that I run in the front combined with the relatively soft tires I use. I converted a long time ago, mostly because the rubber ones available then never seemed to last more than a couple of years. I've kind of lost track of when that was, maybe 20+ years ago, but I've been very happy with them. I even moved them from the wrecked TR3A to my current TR3. I did finally notice some wear last week, so I turned a couple of replacements myself on the lathe. It's amazing how easily that stuff cuts
On the rear, I am running stock Silentblocs at the front eye, and poly bushings from TRF at the rear. Again, I didn't notice any ride difference between the poly and rubber. But I also saw little if any improvement in axle locating. I think most of the deflection is in the springs themselves, so if you really want to improve axle location, a Panhard rod or Watts link would be the way to go.
Unless they are supplying a very hard poly formulation, the original nylon lower front bushings will actually be harder. This was an early factory upgrade (they originally used rubber just like the upper inners). They already last a long time IMO, but you could drill & tap for a grease zerk to make them last even longer. (I also drilled a hole through the bushing so the grease can get into the center where it is needed.)
PS, I see that Ken Gillanders has the Nylatron listed on his web site. Not sure if he actually has them in stock, he more or less told me in 2008 that he wasn't going to carry them any more. But you might give him a call and check.
https://www.britishframeandengine.com/parts1.html
Be sure to ask what is actually in the kit; the kit I got from him "back when" had enough to do both upper and lower on both sides. But since the listing only shows "upper", it may take two kits to do both upper and lower.