If you have a good public library around, they will have the Mitchell's Manuals which should tell you the stock specs. I converted my 225 to HEI and had my Tune-up Doctor recurve it to the following: Curve starts at 900 rpm engine speed, gets 6 degrees by 2000 rpm, total of 12 degrees at 4200 rpm. Vacuum starts at 7 hg, totals at 12 hg for 15 degrees crankshaft. Timing was set to 15 degrees btdc. It ran great until I pulled and replaced it with a 252/4.1L.