Ross, if I can prevent even one person from going through what I did with an MSD RTR distributor I will be a happy man.
Long story - ordered it from Barry R, who set it up with the right gear for the cam he provided. I installed it with a 6 AL box, and fired the engine. It ran for about 12 minutes, then failed. I followed the diagnostic process and MSD told me to send it back.
I did, and here is where it starts to get weird. The problem is not just that the distributor failed, but MSD seemed to suddenly turn into the saddest collection of idiots ever born. Weeks went by and I finally got one of their guys on the phone and he told me the distributor had failed, but they couldn't fix it or send me a new one because they had no parts or replacements, and the shaft in mine had been drilled and couldn't be re-used.
This back and forth took weeks, all the while I was running my old Ford distributor that changed the timing every time I started it. After much arguing about what they were going to do, suddenly they told me there was nothing wrong with it and they sent it back.
I installed it and it ran for 8 minutes before it failed. I called them again and they said they had done all they could (which was really just tell me a bunch of nonsense and then ship it back) and that I should return it to the seller. I asked if they gave return authorizations for failed products and they said they didn't.
I did return it to Barry (although I never did get a refund) and I bought a later Duraspark style one from Faron. It has run without issue for 3 years. I know it is a Chinese knock off, but Faron does seem to be able to make sure they are good before he ships them.
I don't know what is worse, spending the money and getting nothing or being forced to deal with complete idiots. Remember, they couldn't fix it because they had no parts, and they couldn't replace it or take the parts out of a new one because they had no inventory.