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Generally this type of thread laments the disintegration of the factory nylon gear (a known flaw in the late 1970s). A good double-row steel tooth setup (e.g. Cloyes) is the solution. Thus I am surprised that yours failed....
I had the original nylon gears. They were worn badly lots of play. I replaced with the metal. I wonder if they were on to something when the put nylon in there. Wore and yes there were chips. I suspect no damage to the lower end was caused because they were nylon?
Anyway here is a trick to getting the timing chain cover back on. Old timer told me about it. The biggest pain is the gasket that seals the timing chain cover to the oil pan. Loosen the two lower front oil pan bolts.
Put the upper timing chain cover gasket on. Leave the big lower one off. Put the cover in place. Insert the two bolts loosely just near the stubs that are used to line the cover up. Oil up the big lower gasket, get under the car and with a big dull screw driver push the one end of the gasket in at about the 6 o'clock mark then slid it up into place. With the one half of the big rubber gasket in the other side goes in easy just push it in with the screw driver. Its a bit of a trick. You'll have to play with the timing chain cover bolts....you may have to add one or more at the top...or tighen the two at the bottom while holding the cover in place....it likes to pop back out.