well,
www.floydrose.com has routing templates on the site, so that'll give you the dimensions you need.
www.wdmusicproducts.co.uk has the routing templates for the gotoh floyd rose (it's the ge1996tc model, if i remember correctly, that's the good one)
and if you email schaller (google their website, i can't remember it offhand), they'll send you the routing templates for their double locking trems...
other than that, it's just a matter of measuring, i think.
:drink: