Check that neutral safety switch.
Also, I'd bet money that the reason your car is dying and not starting is the MSD. I"m having the exact problem of my L dying and not starting till I sit for a while. I've got the MSD 6A with MSD TFI Blaster coil. I can unplug the MSD and plug back in the stock ignition and it starts right up. Then I can plug the MSD in, run for a few days maybe, and then have troubles again with it dying and/or not even starting. Just sits there and cranks. So I've been running without the MSD for a couple months with no problems. My MSD is only about a year old too
. Plug in the stock ignition and run on that for a while to see what it does. Then try the MSD for a while. Kinda run an experiment. I've heard of quite a few people having this exact problems with the MSD units.