the base plates are steel where there once was the old motors cast iron. exactly right about the angle and motor fitment. the motor slides in between the angle but instead of a hose clamp I am thinking about using 4 long bolts. tacking an unthreaded sleeve and a nut to each piece of angle then threading the bolts through to apply tension to the ends of the angle. i am going to add two sections of plate between the angle to use the treadmills mounting bolt holes. it's not what I was thinking during planning but hopefully this will do the trick.
for cooling I found a small rounded caged metal fan. it is about 4 inches around and looks sort of like the one below
I am thinking about cutting a round hole on the underside of the old motors housing and fitting the above fan inside. then facing the fan so it blows cool air in. or maybe it would be better to have it pull air out?