I bought a used L28 for my 75 280Z. It didn't have a distributor on it , so I used my old one. But when I go to adjust the timing, the distributor
will not turn far enough to advance the timing , lock down bolt is at the bottom of slot . How can I fix this issue

 

On some of the distributors there are 2 adjustment slots. Are they both maxed? If they are or you only have 1 adjustment slot, then your chain is stretched / worn and may need adjustment or replacement.