The bike can be built up with what ever componets you want. I was so comfortable using road bars that I used them to race and commute on a mountain bike once. That may not work too well with the motor and clutch controls but inventive minds invent ways... I do know that down hill mountain bike racers use an 8 - 10 degree bent back bar with a 2 to 4 inch rise and may hit 60 mph on fire road decents. Any thing that is used by serious down hillers; spokes, rims, brakes, tires, bars, frames and forks; should be strong enough for a motorized bike.

Your motor choice looks good but I don't know the seller. His site looks good so go for it. Or go check out the page that lists most sellers ... Find a Dealer & Review
The motor needs to be installed solid and broken in gently for 100 to 200 miles.
Here is a link to some great info on that aspect...
Bicycle Motor Preperation And Care
Use your welder buddy as needed as he will see a lot of ways to make it mount solidly and can really help out. Have fun and make sure you can stop better than you can go. Austin would be a nice place to ride.

__________________
LennyHarp of Lenny's Bikes & Things
http://lennyharp.net
The true value of a man is not judged by what he has, but rather by what he can do without.
"We are what we repeatedly do. Excellence, then, is not an action, but a habit." -- Aristotle