I'll chime in here too. The thrust plat holds in the cam and you need to follow the spec of the manufacturer. I think old GMC is .003-.008" That's all the movement the cam should have. Sounds like the guy put it in flush with the end of the cam snout. Personally I like the aluminum cam gears.
Cloyes makes a lot of stuff. I called them about gears and many, many are available. The factory did some retarding for smog in the 80's and there are gears made specific for that. They also sell one with the 3 settings on the crank gear. advanced, retarded, and straight up. Plus the straight cut gears. Mr. Gasket sells offset keys for this purposr too. Parts for the Chev V8 does fit. Remember the cam turns in the opposite direction if your wanting to move it..For the street I've run up to 6 degrees advanced. Talk about low end torque, it was awesome.
Good Luck
