160 tachometer question

Narrowed down why the tach isn't working on my 160.  The 90 degree adapter is not engaging the coupler pin on the engine.   After taking everything apart it appears the coupler pin is too short.   Doing some measuring it looks to be 1/8 short of coming close to engaging the adapter.   Anyone know how long the coupler pin (believe it is pressed into the rear of the cam) is supposed to be?  Best measurement I get is about 3/8" and needs to be about 3/4".

Unfortunately, I can't remember how I corrected the tachometer drive engagement.  Shortly after posting the question, I dropped a used engine in and found out it had a cracked block so wound up overhauling the original engine which turned out to be the cheaper route overall.   I may have swapped the pin or the tachometer drive adapter from the bad engine.  Seem to remember the original tach drive adapter had something goofy but can't remember what.