I just added the part about checking the clearance as a std. course of prep that I do on a new pump. This also makes sure the bolts are tight when I put it back together. Sounds like the bolts must have been a little loose and I have heard that high volume pumps will the possibility of chatter or vibration. Not sure how true that is just things that I have heard through the years. I never run a high volume pump myself in a SBC, have never found the need for it with the clearances we run. I hope it doesn't knock also. Good luck.
Curtis