Stock small block chevy heads have a 23 degree valve angle unless they've been angle milled. -12 heads are a series of heads with a 15 degree valve angle made by Brodix and sometimes used on sprint cars. Raised port heads are just that, aftermarket heads that have the ports raised relative to stock heads. If you have stock sbc heads you'll need 23 degree injection of some sort, but I'd call the manufacturers tech people and pick their brain.