Timing suggestions for 360?

I have an LA 360 with magnum heads and a cam with a little more lift and a little less duration than yours with a lot more compression (I am assuming your is stock). I am running 17 degrees initial timing and 33 degrees total with springs that have the mechnical all in at 2500 rpm. Vacuum advance only works at light load cruising which with my car is about 15" Hg of manifold vacuum. I used a MightyVac hand pump to set up my vacuum advance so it was all in at 14" Hg vacuum.

If the MP distributor you have was made after 2002 it has both an adjustable vacuum advance and an adjustable mechanical advance. They come set for 24 degrees of advance and I believe brown springs which is close to the 2500 rpm point, this is going to be too much (initial + mechanica l = total). Magnum heads have a more efficient chambers and do not need as much mechanical advance so the typical 34-36 you hear is too much for a mgnum headed engine, 32-34 is where you want to be.

The MP distributor is made by Mallory and uses the Mallory advance mechanism. Mallory #29014 advance tuning kit comes with a bunch of spacers for setting up the mechanical advance with a selection of springs to tune the rate. The instructions include a bunch of graphs so you can select the proper color springs for tha advance rate you want. The $30 investment makes getting the distributor set up or changed very easy.