erratic vacuum

It looks pretty normal for a 282S I would think. You are not going to get a glass smooth vacuum on any cam with a lot of overlap.

1968 Ranchero 390. 060 over,10.5:1, Comp 292H Cam, Performer RPM intake, Hooker headers, 4spd. 3.89 dif. ProForm 750 DP, Mallory Unilite distributor, Holley Annihilator cd ignition system, centerforce df clutch.