|Iain, some thoughts before you set off on a do-it-yourself' spreader replacement.
To continue being a "C&C 27" the spreaders must be "aluminum", and most of the boat needs to remain as built by C&C.
The connection of the spreader to the mast could be tricky, as could the outer end fittings, which not only keep the uppers in position but also stop them from cutting into the main (aluminum) section of the spreaders.
On top of this the spreaders' failure to withstand the very large compression loading when reaching in a blow could lead to the need for a new mast and all it's bits and pieces.............
Others with more experience than me, and with good skills in metal fabrication, might
disagree, but Klacko's $200 offer sounds OK to me.
Alan of SMOKE 1984 Mk V 002