98 base, doing a suspension refresh. Can I upgrade to an S suspension?
 

I've bought coilovers for the base, but have heard the spring and shocks were the same base/S. I have the upgraded cayman sways - 19.3mm - Are there any other suspension differences in control arms, track arm, etc that I can do without touching the brakes?

TIA

The base/S control arms are the same, but if you're after track performance, GT3 control arms are a popular swap. You get way more camber adjustment with them. Do bear in mind that if you're in autoX, it may bump you out of your class. The GT3 front control arms fit in the front AND back of the Boxster, you can get 2 pairs and get big camber adjustment all around or just one for the front, which comes with less camber from factory.

Some bushings can be replaced with polyurethane, at some cost to NVH. Poly lasts longer, which is nice.

The base/S springs/shocks are different, but they are a bolt-on swap.

Perfect answer, thank you. I'll likely do a refresh the suspension and go from there as Auto-X isn't a priority...yet :)

When replacing base sway bars with the M030 sport suspension sway bars - are the bushing different? What about the "U" clamp that holds the bushing?

I got it with a bushing that came with - I believe it is slightly different but don't quote me on that.

I reused the U clamp IIRC.