Bicycle Mechanics - Freehub compatibility: Road/Mountain

I've been swapping freehub bodies and looking for modern (8-9-10 speed) replacements. On ebay and elsewhere I have found more and cheaper Deore models than road group models (105, ultegra). Since road spacing is 130mm and mountain 135mm, is there any reason why I can't use a 8/9 speed mountain freehub body on a road hub? I understand that the wheel will need to be re-dished if a 7 speed freehub is replaced with an 8/9, but other than that and axle length/cones, are there any other possible problems with this?
Thanks in advance and keep spinning.

I'm not sure what you are asking.

I've swaped and replaced some freehub bodies in my time. To be honest, I don't think that I ever even looked to see if I were putting a mountain freehub body onto a road hub or vice versa.

So I guess there is no difference. I thought maybe there was. I don't mess with too many mountain bike wheels and was not sure if the extra 5mm in spacing would have anything to do with the freehub body.

generally you should be able to put most shimano mtn freehubs onto shimano road hubs. known exceptions are the silent clutch freehubs, the shimano road hubs with aluminum freehubs, and the old dura-ace 6/7/8-speed hubs. Some of the mtn hubs with oversized axles may not work either.

So I guess there is no difference. I thought maybe there was. I don't mess with too many mountain bike wheels and was not sure if the extra 5mm in spacing would have anything to do with the freehub body.

There's a slight difference- the distance between the back of the freehub body and the largest cog is slightly larger on a mountain body than on a road body. The mountain body is recessed slightly into the hub shell, giving it a little more sheilding.

I ran into this a couple weeks ago when my cassette body failed on an old Deore XT hub. The replacement body was a road type, and it reduced the clearance to the point where the rear derailleur was barely hitting the spokes. It hadn't done that before the swap.