The harmonic balancer on my '68 302 appears to be an original style though I don't see 3817173 anywhere on it. It has the correct timing location and the "Y" extends all the way to the rubber. I have run it with a minimal gap (1/4 inch?) out from the timing cover and the belts line up. The pulleys are correct though the water pump is a '72 GM. My issue is that the balancer will press against the timing cover before it bottoms out on the crank gear. The timing cover has a 67 date but I thought 67 and 68 covers were the same for 302's. The timing chain and gears have been replaced with a Cloyes double chain (not an uncommon product) which makes me wonder if that is the issue. The crank gear is pressed fully in place and the timing chain is aligned. Is there a certain distance the outer face of the crank gear should be from the nose of the crank? Is the inner hub of the balancer supposed to be a certain length? Laying a flat edge across the back of the balancer, the inner hub extends about 3/8" past. The entire set up has been run without issue up to this point but I'd like to remedy this if possible.