you have to rebuild the lpc so your modchip has access to lad0, lad1, lad2, and lad3 and the proper voltage.
if you take your time and have a decent soldering iron it is not that hard
if your worried about modding your 1.6 theres a new solderless chip the spiderchip
http://www.spiderchip.com/home.html
maybe try that out. Havent heard anything about it yet.
So how what would I have to do to fit a 1.6 Motherboard into a 1.4 case?
On the 1.0-1.5 cases the plastic posts where you screw in the AV connector are two high. You have to cut them to about half size. I just used a razor blade with a handle to cut them but im sure there are other ways. Also there is one screwhole missing on the 1.6 board so you have to break off the metal tab over the plastic screw post (this is what was frying peoples boards when they put a 1.6 board in an earlier case) and cut this post off. Again I used a razor blade to cut it. Hope that helps.