I had my engine apart recently. Without having the timing mark on the front cam I do not know how one would set it up, I assume the cam could be 180 out because the TDF mark on the crank happens two times for every full turn of the cam, but my saving grace was that I never disconnect my front cyl cam. Then again, as long as the TDF mark lines up the front cam, and then TDR (305 degrees later) lines up the 2nd cam, I do not think it matters.
I have a TDF and a TDR mark on the crank, these are 305 degress apart.
I have a VN800, so what I say may not be true for the 750.
can you take the valve covers off and see where the cams are when you get those timing marks? You should be able to see where the valves all are if it is anything like the 800.
2000 Vulcan Drifter 800
Roadhouse classic 2 > 1 exhaust
Okie Smokie intake config
52K miles or so, always going up
Painted flat black winter '12