as far as the grooves, a welder can fill the worn spots and any machinist worth the tools he is using can get it back to specs. Atleast this was the case when I worked at Whistler Machine Works. The guy I bought my boat from needed a new shaft so they just made him another from a bigger shaft turned down.
19' Skier 351W PowerSlot Deluxe
Long gone is the Trans AM
waiting for another