Even though the problem is fixed can't believe the timing was truly that far off. Makes me wonder if the outer ring on the balancer has slipped or if they lost the woodruff key between the crank and balancer and the friction between the bolt, balancer and crank is keeping it there. If the ring slipped that probably why the timing tape was there in the first place. Since the 383 is internally balanced not a huge issue until the ring slips off and goes through the radiator. I would check these couple of things when I get a chance if I were you just to be sure sounds like shoddy work and I just don't trust anything touch by a shoddy mechanic and if I find one thing wrong I go through everything they touched.

BTW the centerline in my 509 cam in my 383 was off from the get go had to degree it into get it on the right centerline then advanced it a bit for a better setup.