I have done no changes to the a-arms or swing arms. As far puting the 400 in it all you need is the motor mounts for that year or style frame if you are getting the 400 out of something around that year like expolers or the sport the mounts on the 400 will work fine. I used a pipe for a 96 exploer it was a RCR pipe an it fit good. I have the 250 in it now cause can't have My 98 scrambler down an not running. The Plastic bolts on easy on the rear of the plastic when you flip it over for the scrambler frames there is at the bolt holes it is thicker an need to grid it down flush. The shift handle dose not line up with hole for scramblers either when I had the shifter I just cut it out for it.As far as it flying it dose it pretty good have put alot of air under it before an not afraid to do it agine. If ned more info just ask