12G295 is perhaps the 'ultimate' head for small bore A series, IE not 1275 or variants. They crack like anything around the valves so get it magnafluxed. Put it on Ebay and you'll get heaps for it because the Mini Coopers used it (99% sure). Dave Visard wrote a lot about them in "How to modify your Mini" IIRC
Andy.
PS this is forum is mostly about the bigger Healeys, you might get a better response on the Spridgets board.