Vacuum question!

Those numbers are fine for a 4" arm. I'd expect to see a slightly less number with a better carb. 750 is just plain too small for a long stroke like that. In "std" Holley cfms, I'd say at least an 850 on it, in Demon, Avenger Holley, or "wet flowed" the number should be 800 or larger. The cam is mild, but perfect IMO. If the heads were milled for the open chamber, the 38° number may be ok. If the smaller chambers are run with pump gas (at least the 10% ethanol and 92-93 ocvtane numbers we have over here) and properly designed quench, the low 30s will be the highest you need. A recent big block with Indy SRs likes a max of 28° total. I had to make a bushing for the MSD for that...lol. Like Dave said...you want max pressure at about 20° after TDC in crank degrees. Lower octanes burn faster.