another no start issue!!!! (more than a little frustrated)
constant spark is an indication of a bad control module.
I would stick with your points distributor until you get the engine no start sorted out.
I can't recall which direction the rotor turns but rotate the distributor about 10 degrees in the opposite direction the rotor turns. This will advance the timing and should make the engine start easier.
if the engine was rebuilt you will aslo have to consider that the timing chain was not installed correctly and the cam timing is off by a tooth or two.