If you have a spare/crap head, saw it apart and use it to see how far you can go when you port your cylinder head. When I searched for a good A15 head in my garage last week I found 11 A-series cylinder heads!!!!
This was Reg's Shellsport winning 100A. It was built in Japan by Nismo. It was also rallied in the Heatway International Rally of NZ by Leo Leonard. The car featured an A14 with mechanical fuel injection. The wheels are 14" 3 piece Gotti's.