The marks align, sure. But is the piston KNOWN to be at TDC when the marks are aligned? Probably, based on what I'm seeing written. Putting in an HEI is pretty straightforward, you just need to run a wire from the "IGN UNFUSED" terminal in the fuse block (if a '63 has that), and remove the coil and it's power wire, and the yellow wire from the "R" terminal, as well. Though you could leave the wires in the harness and tape them back in case you wanted to go back to original. The rebuilt 6 cylinder distributor is about $40 at NAPA. I can spend all your money, if you want an HEI, go for it.
Looking at your old distributor, I'd bet that it would help, though one with a better lobe condition might be all it takes.