just rebuilt runs bad

You are getting very close, From what i heared the engine sounds great, you can try a point distributor for testing, because you shouldn't need any more then 38* total, Now on that distributor, i'm sure its the one i ran on my last 360 & i loved it, remember it is "totally" adjustable, from the curve/how fast it comes in & you can tighten it up, It'll come with bushings, I had mine with a total of 20* advance, all in at 2200, now my cam was small, so it idled great at 10*, If yours is good at 15* initial, I'd set it up for 20* total advance, then you can run it 16* int., 36* total, have it all in around 2200, test from there, do not run any vacuum advance, just plug the ports, MSD/Mallory/Crane boxes can/will advance the timing around 3-5* from other ignitions like stock HEIs/ECUs ect., even points, but that doesn't mean you run it 3-5* advanced over where it would run best, IMO your very close now, work on setting up the curve, the instructions will show you what bushings/springs too install for what your after, They normally come with blue/silver/gold springs in pairs, this will adj. how fast you want the total to come in, the bushings are for the total amount you want.