...or modify the idler mount. Factory recommends ovaling the hole of the mounting bracket to alter the plane of operation, then welding a washer to the bracket to lock in desired location. Also be sure to shim steering box a similar amount.

you also could consider adding a shim between the motor mount and isolater to slightly lift the engine.

I'd be cautious that banging away on a header tube to clearance it doesn't break a weld at the flange on the head mounting surface, if you go that route.