That sounds like it will be a problem. You didn't say if you have gas or diesel model. Might work on the diesel but probably not on gas. Two issues that come to mind. First is that the existing hitch is probably not rated for that much weight. Second is whether or not you'd overload the rear axle and at the same time, pull weight off the front and upset the steering.
Here's a link that will help you determine how much you'd be adding to the rear axle.
http://cruiserlift.site.aplus.net/siteb ... amrev2.pdf
Need to weigh the coach to see what you currently have on each axle, then use the calculations to see if you'd overload.
Cruserlift and others sell lifts to to what you want but most won't sell for installation on a gas mh as the rear portion of the frame isn't heavy (strong) enough to bear the additional weight.
Good luck,
Dennis