Distributor setups for L78 or L72 engines?

[Jeff H]

The vacuum reading is around 14-15 at idle. It's definitely a low idle but the car has no problem at this idle speed. If I advance the timing a little I will get some pinging. If I turn up the carb idle speed it tends to get hung up a little so I like it where it's at right now. The carb is a tweaked Holley 750 that I don't really like with the modifications to it so I'm trying to get an original 4557 rebuilt. The engine has some 71 oval port heads so the compression is probably lower than a stock L78.