Originally Posted by TopElement

Yes, I have replacement bushings for those 3 locations too. My car is a Nismo model, but the front damper lower bushing is lekly the same size.
Lower control arm bushings definitely make a difference to suspension feel and response, with a slight increase in road noise.

Delrin/aluminum was chosen as IMO it's the best solution for rubber replacements for single axis movement. Wherever polyurethane works, Delrin is better in terms of performance. Polyurethane is good for mounts, but not moving parts since it sticks-slips-sticks-slips (stiction). This is not very smooth, often causes noise, and is still compliant similar to stock rubber.

Spherical bearings have a slight advantage over Delrin with metal sleeves as far as precision and smoothness. They do require a little more maintenance (cleaning, lubing), transmit more noise, and require replacement when they wear.Converting stock suspension parts to use spherical bearings is also more labor intensive and expensive. Since bearings come in set sizes that likely don't match the bore where an OEM rubber bushing was, it requires adapter sleeves and then requires spacers on each side to center it on the mounting pin/bolt. With Delrin parts, the actual bushing is machined exactly to the size needed and reduces part count and price.

I'll work on getting pictures of all the upgraded suspension parts on my Z. There doesn't seem to be much interest in these type of real performance upgrades for these cars, so not sure if a large run of production parts will be made.