Rebuilt 318 Refuses to Start

you said MSD ignition, but didn't specify if that is the control box, or distributor or both. The pic, above, showing the quill shafts slot orientation, is for an earlier LA. engine. And now you tell us it's a Magnum small block. They are different. For some reason, the orientation is different for the Magnum distributor. But we don't know what dist. you're using.
I think I'd first pull all the plugs, and check each cylinder for compression with a compression tester gauge. This will give you an opportunity to either replace the plugs, or totally clean them with brake cleaner, and compressed air, because you just now disclosed you heavily flooded the engine, first. For some reason I don't fully understand, heavily flooded plugs never are quite the same. The fact that the block, and maybe the heads are cut, coupled with the "big" hydraulic roller cam(not degreed in), begins to send up red flags in my head. So it would go a long way, in my mind, to know what kind of cylinder pressures we are dealing with. The next thing I would confirm is TDC. For me, a screwdriver in the spark plug hole is not accurate enough. Beg, borrow, or rent a 3 or 4in travel dial indicator, and make absolutely certain the mark on the damper is really TDC. The other reasons I'm a little sceptical is 1) It won't even start with starting fluid, 2) at some point, Ma Mopar has had timing covers with different timing marks, and at one point dropped all timing marks off of the cover and dampener. Had you degreed in the cam, the first step is to confirm the TDC marks, which would clear up any questions later on.