hi everone new guy with some questions

If it has about a square foot opening, it should go no problem. It looks like an in frame kit will fit.

The Madwagon is almost the perfect bike to be motorized (frame mount engine). It's made heavy and comes with strong MTB brakes.
A couple of things to watch-
The down tube looks oversized so you may need a to get front motor mount for oversized frame tubes or you can make one with a muffler clamp.
If that lower top tube interferes with the carb, you can alter your intake manifold by sawing it in half and use a heater hose to make a flexible section.
There are many posts on this site about both issues.