Rewiring my EFI Magnum - 1970 Dart Swinger

Leaving one empty on this connector for now until I figure out the tach situation. It seems the Magnum PCM sends a signal with half the pulses my tach is expecting. I had a guy tell me he put his aftermarket tach into 4 cylinder mode and it worked, but I don't know if my tach has that option. I have the rallye dash tach from Classic Industries, which might have been designed to only work with 8 cylinder engines.

I can pull off the cluster and have a look at it, or I can just splice the tach wire into coil positive like I had done before. Does anybody know if that tach has the switching for 4 cylinder mode?