No start on rebuilt 360LA

This is dead on listen to this guy he knows what he is talking about! He walked me thru my electrical issues on my dart over the phone late one night and I did the break in the next morning! DEL knows his stuff and is the one guy here that is right 100 percent of the time! Well 99 percent lol :lol::poke:
Absolutely- the initial setup MUST be right to get it to fire up immediately. You don't want to be endlessly cranking on a fresh cam.
But there's multiple issues here- with a ready to run distributor AND a 6AL both on it (no idea how that would even be wired...?) you've got two different ignition control systems trying to operate: a single-fire and a multi-spark... They're most likely fighting each other. Get rid of the 6AL and just use the ready to run distributor to get it going (wired per MSD's instructions!), after making sure your initial is set correctly.
If, after setting your initial correctly; and getting a single ignition system wired in correctly, it's still not starting, you've got to question whether the cam was installed correctly- a tooth or more off will also have similar symptoms.