To run aftermarket rear wheels on a 50cc Maddog you have a couple of options.
1st option is to get the Monstergy6 12×8 hub kit and a 12×8 wheel. This is a very good kit And runs the rear true centered.
Another option so you can run a 12×7 3+4 wheel is buy a Kymco Hub
Kymco Hub
The kymco Hub is 4×140 so you will need to buy a 4×137 wheel and take a few strokes of a file to widen the hole to fit the 4×140 hub. The wheel will need to be 12×7 3+4 offset 4×137
This is an awesome wheel that you can run with this hub. You will need to run it flipped backwards.
http://www.amazon.com/gp/product/B00317DEIY?ref_=cm_sw_r_awd_cJXIvbREFXQ7F
Another option is to run an ITP Delta Wheel in 4+3 offset flipped backwards. On the stock hub. This will run about a 1/2 inch offset to the right.
ITP Delta Wheel
