Get an edge trem and rout out the cavity. Ive done it to a couple guitars and its very easy to do. The only thing is you will lose some visible material that will make the cosmetics of the guitar look choppy. If you need pics to see what I mean, just PM me. I dont have time to take them now.
I've used a dremmel and some sand paper to fix a cavity for retro-fitting an Edge trem. You may not get the neatest job done but it does it. I'd just get a Gotoh Licenced Floyd Rose for the job though. Should be a direct fit.
yeah a Edge III bridge but when I try to dso some whammy work the freakin bar comes out of the socket ....it's like it's not long enough. I don't have that problem on my 1550... I changed the pickups in it so it sounds and plays good so I am happy with it except for that.