Get a gear mini starter or GM high tq starter both are easy to find and work. The gear starters are best they just work every time. The GM starters go bad if they turn slow. The more it does it the faster they wear out.
My poncho would not start with stock gm starter when hot. Not sure how mouse fink got his to work with 12:1 but I never had any luck with the stock starters on larger high compression engines. Maybe mouse will help us both out on that one. Once i get the timing where the engine makes power with a big pontiac they always start slow.