Mark

Nice 720 w/pony start. Straight pipe? Can you still hear?

I don't think a 720 would ever put out 70 hp. I'd consider dropping to 6 shanks & respacing them, starting w/putting 1 shank in center (or nearly so) of each rear tire. Then space the remainder accordingly.

The only problem you might have after doing this is having a really wide frame that may bother you next to fences. But-maybe not. Take a look @ that idea.

Good luck & report back if you get it done & have time.