What's a good set of springs to order for these heads? Their 915HP's, virgin, have been cleaned up, going on 440 six pack, 509MP cam, .030 trw domed,new Elgin factory length push rods, new Mopar factory style rockers, new CompCams rocker shafts, Rhodes lifters, and I believe they're the stock valves on the heads... my old heads seemed to have held up okay, 906's, but had a bent/stuck valve and had these on the shelf. thnx