Originally Posted by wwoodruff

They use stock 7.5 arms.

I am in the middle of converting a 777, everything fits, but you will need parts from the 7.5 and GT2. Also short shorter shocks for the rear and on-road springs front and rear.

It does not look like anything from the MP-9 will work with the older cars.

I converted a mugen MBX5 once, and used the stock shock towers with Ofna body mounts and a modified front bumper.

You will however need to do some milling for the 2 speed if you plan to use it. I had some custom made motor mount blocks made so I could use a shaft start system. I think the GT2 mounts are standard type now, so that is not an issue.

Unless you plan to race, any engine you want.

Have fun.