Why would you want a mouse from a heavy truck? The valves and heads are designed for heavy pulling and high exhaust temps (thick stems, etc). I can't imagine that profile fits an RX-7 retrofit. The same engine out of a light truck or SUV would be much more suitable, in my opinion (and a lot more common).
I'm not trying to pick on you, I'm just wondering what I am missing?? I couldn't agree more about the 267...after all, all the cast-iron small blocks weigh about the same no matter what the displacement.