Due to the angled seat tube, you'll probably find you will need to cut down a seat post, or at least cut an angle into one of your post is longer than the angle will allow to fit at the height you want. The og post was short and angled. You won't want to run a dropper as the drop will move your saddle forward.
The shock is the Achilles heel, you can't easily replace it as it's a trunnion.
There are options.
Risse. Spendy and US based so shipping and tax makes it more so.
I did have a fox trunnion on one of mine. Designed for the job so fits if you can find one.
Another option is a fox or manitou from a Cannondale Jekyll. Needs the trunnion modifying (shaving a few mms) and customising of the trunnion bolts to fit the travel chips, but it can be done and you get a much better shock than the stock rs.
There are modern trunnion shocks which may fit, but I can't say if any will.
I built mine up using m972 xtr and it looked awesome and was a nice ride, but too much bike for my riding skills
A set of spin wheels look amazing on these frames.