I have a 350x that needs rings, I also have a 250x engine, parts of a 300ex engine, and soon maybe a full ex engine.

The EX seem to be the best due to electric start, reverse. Sucks that there's no backup kicker, though.

I originally wanted to use a 250x transmission or full bottom end and 350x top end if the stroke was the same, as I want reverse.

If I use a 300ex engine, has anyone found a way to use a 350x or 400ex (will those full engines work?) top end to make the displacement larger?

Hate to go down in displacement when everyone seems to want to get more.