I've been working on an adapter plate that I want to make out of aluminum since January. My biggest problem has been trying to get a machine shop to actually make it, there not to interested in 1 off jobs, but if you had your own cnc then it would be doable. I used a technique using a large sheet of thick paper and a lead pencil to get the outline of both engine and transmission holes and then passed that onto someone who knows cad to produce my drawings. Keeping the center point is crucial and make a working template out of mdf first to make sure it fits.