Weed Dog,
Sounds like you have a good project there. Two thoughts: If you are willing to go to dc, you might look at Surplus Center
Surplus Center - Hydraulics, Engines, Electrical and More . They have a lot of dc motors, including a 1 horse 3400 rpm 120v dc motor for $40. You might could use a 120v dc motor and a big full wave bridge to make a corded 3400 rpm mower. I'm no electrical guy, so there might be other parts needed, but I have used such a simple circuit at lower voltages. I saw bridges rated for 35 amps at 600 volts selling over at American Science and Surplus in Milwaukee for $3.95 each (not a typo) last week.
One last word. I am about fifteen minutes south of daox in Menomonee Falls, with a basement full of hobby machine tools. If you're in need of a jackshaft for your current setup and can get over here, I can probably turn up something for you. I've got stock in my shop to about 2" diameter. I am currently among the economically independent (translation: got laid off Friday) so I have time to do some tinkering. My electric rider project blew up last year along with the gearbox on my old Toro, so maybe I can pick up some ideas by helping another tinkerer.