1991 red-block B230F swapped into 1987 745 some years ago now failed smog only for Balancer pully rubber broke loose so timing cannot be checked. Had it replaced by employees, however they crushed crankshaft timing sprocket drive tang. I replaced both and tensioner, belt, etc. kit, even new belt guides as one was bent. Also checked distributor and coil. Would not start, sent to local independent who found air mass meter fail so now starts but rocks violently and has a screech-screech from head area. We towed it back to my shop. Disconnected all accessory belts and left covers off. Could not determine source of screech-screech with stethoscope with cam cover off. After running through things in FAQs, any ideas before I do an engine swap?