Come on guys, lets give him some encouragement. This is Stovebolt, not VCCA. When I took machining class in evening adult education the teacher told me "Anything you can imagine, you can build. All it takes is time". That gave me the confidence to take on some challenging projects.
The only critical part of this project is keeping the transmission input shaft and the engine crankshaft on the same axis. That can be easily accomplished by machining a hub-like fixture that bolts to the back of the crankshaft and has a rearward protruding transfer punch that contacts the adaptor plate as it is tightened up to the back of the engine. That will center punch the plate to establish the crankshaft and transmission axis point on the adaptor plate.
I have a 2004R in my street rod roadster but I forget what the front of it looks like because I installed it about 7 years ago. Anyway, a centering device can then be machined to fit the front seal area of the transmission and fit the crankshaft center previously located. When the trans is in contact with the adaptor plate with the transmission axis and crankshaft axis exactly matching, a transfer punch will locate the bellhousing bolt hole locations on the plate.
As for a "Properly machined adaptor" mentioned by Andy, a very good friend of mine bought an adaptor plate to mate a 2004R to his '63 Studebaker Avanti engine. It didn't even come close to being an accurate part and required major reworking by my friend before it could be used. He was very disappointed.
If K10 makes his own plate he will have a lot more bragging rights than he would have if he bought one. In fact if it works out, he would then be able to use it a pattern to make more for other people.