Any reputable shop that specializes in this sort of thing will have a formula table to refer to. I had this done to my 390 awhile ago and he just pulled out a well worn piece of paper to refer to. He told me the guy that sold him the shop was an old Flathead-nailhead-rambler guy that could cite the figures off the cuff....Russ __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com