If everything else checks out fine, and since you were considering something different....... it might be worth trying something else.
I’d def have a proper cranking compression test near the top of the list. Engine warm, all plugs out, wot, battery charger hooked up. Test at 4 pumps, and max pressure(like 8 pumps).
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads