After much measurements, thinking, e-mailing etc... I have a plan for the motor adapter (Rob/RKM has been patient and most helpful in this). Recall I will keep the clutch/flywheel, so a well designed and well balanced coupler is essential.
Here are some plans (made with Google SketchUp 7 - free!):
3D Top View:
Here is the Browning split taper P1 bush (rough specs here http://www.drillspot.com/products/51..._Taper_Bushing
I will be very space limited with a Warp 9 motor in this transverse setup - there is only 20 3/4 " from the transmission face to the passenger side frame (in fact I may find I have to cut/shorten the tail shaft to make it fit - using an Impulse 9 is also an option, but less performance so trying this first).
This coupling design uses a reverse mounted Browning bush - everything can be tightened/loosened from the front, which means the coupler can be pushed as far as possible onto the shaft (which saves room). The standard taperlock design cannot be used here - it would require grub screws to be put in from the motor side, and if reversed (ie flange side out) then the weird pilot bushing cannot be added.
I choose the Browning P1 bushing, as it is the smallest bushing which offers keyways on both the inside (between the shaft and the bush) and the outside (between the bush and the adapter). The shorter H bushing would save more room, but no outer keyway is available (so there would be more chance of it slipping off - I don't plan to take this off again).
To suck in the bush into the adapter, 3 countersunk bolts are used (another advantage of the P1 size - smaller sizes only have 2 bolts and may result in more runout when tightened). To remove it, 2 (out of 8) holes for bolting the flywheel will be tapped all the way through, so I can insert long bolts and push off the bush.
After designing this (of course), I noticed something similar (without the fancy pilot requirement) at:
All suggestions welcome! Off to the machinist soon...