What year did 318 motor mounts change?

Several reasons. I wanted the 45 extra cubes, I wanted to run the high swirl 302 heads, and I couldn't find a set of 273 pistons.

You can run the "302 heads with the stock 273 pistons (2 bbl). Not sure if they'll work with the 4 bbl pop-ups though.I'm doing that right now.