You can just squeeze those thin metal frames in a bit with channel locks and the front mounting block will fit right on.
If you need it longer, you can get a second block and longer studs from gasbike.net, $15.
Personally I like to paint the parts but the point is you have a mounting block plus the studs to keep the motor in place.
I have never been a fan of drilling the frame and just using a single bolt.
You need the support on the right side of the frame because your motor is constantly trying to go to the left. A single bolt through the frame is just going to bend the hole and move eventually.