Alloy "S" Calipers

Are there any alternatives, do I have to replace them with the same calipers...what is the market for rebuilt/used ones. How can I tell if they are rebuildable on my car..I know "If they're rusted or pitted" but to what extent is considered "rusted"? Will I have to remove them to determine whether they can be rebuilt?

Thanks

Vertex Automotive 305-442-2727 offers rebuilt alloy calipers for $134 each. I have the alloy calipers on my car (an early 78 911sc) and have not needed replacement yet, but I would be curious if anybody knows for sure if the "m" calipers will retrofit.

I have since learned, from Bob at Pelican Parts, that the "M" calipers are indeed a bolt on replacement, they offer them for like $200 new or $90 rebuilt.

Thanks for the help!

Whoa!! 'A' calipers are a direct replacement
for the 'S' alloy calipers. 'M' caliper has a narrower bolt pattern and will not fit.
I would rebuild the 'S' caliper. If you don't want them, let me know and I'll buy em.
J P Stein