JRP2 (oops I mean 3)
Race glides ($2000.00 -$4000.00 depending on what you put in them) regularly push 8-10000 rpm with 800-1000 ft lbs. But that is only for a 1/4 mile. They do get a bit hot, they do get torn down regularly, they do get new parts regularly. They are not often driven on the streets regularly.
For regular driving with a generic $1000.00 (home built for a lot less) beefed street glide (see TCI), my guess is 7000 rpm regularly would be a max limit. The clutch drum and planeteries in a glide are not that big in diameter, but at even at 7000 rpm your going to be close to the limit before they start comming apart. Maybe going to the available exotic metal parts, better bearings, then up the oil pressures and increase the lube flow for better cooling, Now we are back up to BIG money.
I'm assuming your talking about a converterless setup. With a torque converter you wouldn't want anything bigger then an 8 inch (big money) and even that at 11000 rpm
yipes !!! I'd want some THICK metal around it. Also again BIG money.
You can buy off the shelf specal explosion proof bell housing and trans case castings, but bring money.
I've looked at the available A/C motors (like the Ford/Seimens) that turn those kinds of rpm, in conjecture it looks like the output shaft Ford is part of a gear reduction unit.
In the long run I think a converterless, standard glide with a 2 to 1 reduction unit placed in the area where the converter would go well with a high rpm motor. This would allow you to stay away from those expensive race parts.
P.S. I still want an AMPhibian.