you should be able to fire the msd with the haltech ignition output.........
Make sure you have the Nissan trigger setup and that you are using a distributor wheel of the z31 or maxima.
when you take it out of the z31 make sure to mark what side is up so that it is installed the same way in the 280zx distributor.....
if you don't have the z31 distributor wheel you can only run batch fire which is fine if you are not using individual coils..... if that is the case you only have 3 wires that need to be connected to the distrib...ground,power,signal
I will try to get the pinout for you tomorrow
the haltech only puts out a ground signal to the white wire of the msd
if you want to test the msd just
remove the coil wire from the distributor and ground to manifold
connect msd wiring as in the instructions and ground that white wire for a moment
you should see a spark at the coil wire
if not then the box is bad if wired in correctly
hope this helps
Paul