You can usually find the right pulley assembly from the old
motor sitting in your driveway. The main problem is that the
electric motor shaft will probably be a different size and
require some grinding (of the pulley, not the shaft) to make it
fit.
Now onto mounting those other component...
We found that using plywood was a great way to cut and fit
different locations and designs for our charger and controller
assembly.
Just check around and get everything to fit. You want to
make it look nice so take your time. A jigsaw works well for
cutting complex angles in the plywood to get it to fit snugly
in place.
After the plywood is fitted where you want it, you can
securely bolt the components to it.
Again, remember to get the batteries in place too. It might
take some fiddling but it is worth it.
While we were designing this part of our electric car we
realized how difficult it must be for car designers to come up
with efficient designs for their new cars.
Fitting all that stuff in there can be difficult, but it is a fun
challenge in the process too, knowing that you are nearly
done.