HELP, sb magnum 360 pushrods

Can't tell you for sure, only what my experience has been.

Running R/T heads as well, with Hughes drop in roller lifters. I am running a set of SB Ford pushrods at 6.881" long, but I haven't started the motor yet. Factory pushrods for a Magnum are 6.9" long, the shorter ones I have put my preload at about .080" deep. According to Tim at Hughes, that should be about right. If it isn't, I am going to swap some 6.821" Comp pushrods in and see how that works.

Don't know enough about your setup to say what works. Just relaying what I did.