Never had a stock D-port head flowed, but seen many 67-70 heads.

Gon'a stir the pot a bite

Things i've noticed;
The M/T RA heads usually had smaller chambers then A/T RA heads.
Same with FB-GTO's vs big cars.
About 72 vs 75 cc's, or anything in between.
Had a set of 48's at 71.
Even had a set of 12's at 69.
70 RA D-ports used different valves and springs then 68-69's.
As of course the 67's.
Each year the casting became alittle cleaner then the privous.