I have the opportunity to buy a set of five, yes only five 90mm domed Mahle pistons with valve notches. I am assuming that these are the factory RS 2.7 pistons.
I can get them cheap - is there any point in buying 5? Will I ever be able to buy a single?
I can also get a set of good 90mm Nickie's cylinders from a CIS car. What are they worth and are they compatible with the RS pistons or J&E's?

Im pretty inexperianced, so any help is appreciated.

Also, is there any market for stray 2.0 liter and 2.2 liter "S" pistons and cylinders?