The SP designates its a replacement for the 109 motor definitely not a prototype for Stage anything.Untill you find a fat webbed SP and add beautiful splayed caps nice job who ever did them.Not all the SP motors had a thick main webbing.GM Holden had some nice stuff in there light duty commercial trucks like cross bolts.Would'nt have believed it until I seen them myself.I wish you nothing but the best on this build.Take Care,AL.