If your friend has the capability to measure seat and face runout use the same angle for valve face seat. Shop manuals advise using an interference angle because the quality of valve jobs can vary greatly. Pontiac recommends .002 runout for seat and valve. An interference angle is not needed with accurate machine work. I use <.001 for the seat and <.0005 for valve face. I once had fix a valve job on sbc that had .008 seat runout. An interference angle will pound out within 100 miles. Also a 45 degree seat will wedge tighter than a 30 degree seat.
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There is no such thing as too much cam, just not enough engine.
1966 GTO - 11.31@119 (3478 lbs) in 1979
1967 Firebird - 9.73@138 (2940 lbs) in 1986
400 cu in / 295-298 cfm RAIV / Lunati Cam 278/283 - .704 lift/5.13 gears
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