Hey Olycarguy,
This was the 1st Mazda to not have a rotary. Historically speaking, that is significant. You should rebuild the 1800 & run with it. It was not a Bertone design, but a Guigiaro, another Itallian design house. Same guy that designed Alphas & many other beautiful cars. This is the same engine as the early Ford Couriers, so use 1971 or 72 Courier at the auto parts store to get what you need. The side draft carb was one of the reasons it made good power & you could easily add a second of you have a good machinist. These didn't handle that great, but they did have posi traction, at least mine did. Won't be a great track car. Better restored as a grocery getter. They do not have a high demand & do not sell for much more than what you paid. Typically around $1000 for one that runs. Getting harder to find though. Please, if you decide not to restore it, get in touch with me.
dkcomet@yahoo.com. I have been trying to find a wagon & have not had luck. The last one I came across was for sale cheap for a long time & by the time I found it, the guy had it crushed & was selling only small parts. They are much more common & popular in Australia, but still not too many.
Cheers,
David