Reverse cranks are still available from Fox for most of the engine line.
Had a CW turning Fox 35 - factory shaft - in an All American Sr years ago. Upright bellcrank (pushrod outboard of pivot, elevator horn underneath) and it didn't need tipweight. ...even with that exaggerated longer inboard wing... Torque reaction on the motor mounts seemed to lift the inboard panel enough.
Back then, there was a decent choice of LH propellors... Now, I've seen "pusher" props (the gray ones, at least in 9-6 or so) that have the airfoil shaped to push when turning CCW, not pull when turning CW. Makes a difference. This may be the choke point on doing a reversed rotating pair...
The CW Fox 35 ran just about identically as my other CCW Fox 35s. The worst thing about a CCW engine is propping it. If the model is on its wheels, you have a tendency to punch the pavement... If you're using your flying hand to hit the prop, that could make a difference in how well you fly...
If you find an engine you want to use, that has an LH shaft available, I'd recommend making the change before break-in. Break-in cuts some metal and polishes fits. If you do that really well, you'll have a good engine that lasts. Changing rotation direction on an engine that was already broken-in t'other way means you'll have to cut and polish more metal to break it in - again... May not mean much, but then again, it might...