or you could have gotten a stock old points type distributor for next to nothing and put an electronic conversion kit in it for $35- $60 bucks depending on where you bought it from and dropped that in it with out any modifications....Its funny that you just posted this cuz I just got home from altering my fire wall for my hei. I will post some pics tomorrow night for you guys. And yes it would be easier to buy a Msd unit if you wanted to spend the money! My buddy gave me a HEI unit complete with plug wires and all so thats $0.00. I had some sheet metal laying around and my room mate happens to be a professional fabricator. So with those ingredients we went for it. Basically you have to move back the firewall back a good 1 1/2". We went 2" so I still have room to get my hand back there to adjust timing. Its a good 3 hours of work with the right tools and lots of skill... But It was free.
HEI's fit in some early novas without mods. Like mine. 64 with stock HEI no firewall mods. It's close but doesn't hit.