Did the nylon gears come in low deck 383's?
When I was a teenager I had a 383 '69 Coronet. Constantly got towed home due to loss of oil pressure.
I was told the oil pickup and/or oil passages were getting clogged with nylon pieces. Sold car and never opened the engine up to look.

1970 Challenger, all aluminum 528 Hemi, HDK suspension, Tremec 5 speed manual