The typical 2403 Delco distributor gives about 12-14 distributor degrees of mechanical advance so the motor sees 24-28, with 24 being the more common. So with a stock distributor, if you wanted to get to 30 degrees advance total, you would set it at 6 -8 degrees of advance (at the flywheel) and yes, a dial back light is pretty handy. Now all of that centers on how accurate your flywheel bb is.
You put one of tom Langdon’s v6 hei distributors in. So you will need to sort out total mechanical advance for that distributor. If it’s 20 total (that is 10 degrees at the distributor) then you can easily get 6-8 initial and tinker from there to see what your motor likes. 10-20 is a lot for a stock motor so I would not start there. just go slow and bump it until the motor tells you it’s to much.
