Finally added wheels to the RS drawing. I was sorting out the distance between the front axle center line and the engine. Also I wasn't sure what wheel size I was going to use for sure, or how much room I needed between the live axle and the 633 axle.
So for now here is what I came up with. 42" outside width. Front axle center line to front of engine: 6". 1" between rear of engine and front of 633 transaxle. And from the 633 axle to the live axle is 7". The rear swing arm will be fairly short with this setup but shouldn't be an issue for mild rear suspension.
At the moment, I'm not 100% sure on steering placement. I figured 6" would be enough room to fit a golf cart rack and pinion between the engine and front axle line. One possibility is to put the rack in front of the wheels and then you might be able to move the engine and transmission forward a few more inches. But you've gotta keep it back far enough so that the drive pulley clears the front tire.
To get more room in the rear, the 633 could be turned upwards at an angle and the 633 axle moved forward somewhat. But this would bring the center of gravity up and also create some possible lubrication issues. The shifter would be at an odd angle too if I went too far. But it shouldn't be necessary to tip it up more than stock.
Front of tractor to the left. The 633 is staggered to the right of the machine to line up the pulleys, leaving room for a fuel tank or battery on the left. The opposed flywheel also counter balances the off set transaxle since it's at the far left of the frame. About 1.5" is left for the swing arm attachment on the right 633 axle (which will need to be cut down of course). Everything is going to be very snug, but (hopefully) easy to get at.
Current plan specs:
-Wheels (front and rear) 18 x 8.5 x 10