Mike I have raced 455 for a few years(lol) and have run the 350 the last year and half because the 350 make's alittle more hp per cubic in. I just got a new cam for the 455 and should have the 455 back in car soon. Ok back to your question, I run 38 or 39 degrees of timing. I use the MSD Dist. with all timing in at 3000 rpm in both motor combo's. The reason your stock 455 motor has a 5000rpm range is valve float from lifter preload (AKA) pushrods down in the lifter . I do not run any studs or girdle's for crank or valvetrain, RPM wise I spin my motor's in 5800 to 6400 rpm with 4.10 or 4.30 ring& pinion. Hope this help's you out, If I can help in any other problems e-mail me your questions at
rowdyboys@comcast.net JOHN KEIHN 3954 G/sa-K/sa