Unported head quickness?

Early 80's, I had a '71 Duster 340 auto w/ the following,

Stock short block w/ M.P. 284 -.542 Solid Cam
Stock J heads w/ fresh valve job and seats cut for M.P. Springs
Edelbrock intake w/ 750 D.P. Carb.
Reverse manual valve body & Vitar 4000 Convertor.
4:88 Gears in rear end.

Ran 12.0's all day long w/ a best of 11.88 - 114 mph.

Glenn