Dirt track vent..

Looks to me that a W2 headed 360 would be the hot ticket. On a metric chassis.
You might want to rethink that. The W2 heads will cost you a small fortune. I ran them for awhile then got a set of W5 because I could use all of the hardware. Plus they will never let you run them now. Hell you might be better off with a magnum motor setup. IDK, been along time.