I have never been able to use the VR pickup AC voltage output from a pre-1985, non-computer controlled timing distributor to trigger an MSD box directly. The signal is not strong enough and needs something to convert it, either the stock ignitor or a GM HEI module.
FWIW, there are lots of Datsun guys ditching their ignitor when running a 6A/6AL. Not sure what Nissan did different but no one has reported any ill effects from it? In fact, you're the first person I've heard of that did have a problem with it? Kooky...
But since I haven't personally done it, I'm inclined to agree with keeping it.
I've done it for years with L28 distributors...just dump the black box on the side of the distributor and hook the leads directly to the mag pickup wires on the MSD box. Works like a charm!
However, the Toyota signal output is quite weak and won't trigger the box directly...at least with the 18R-G, 20R, and 22R/RE distributors I've tried it with.