Thor kit looks very nice, but I've heard of a few bad experiences from people dealing with them (can't vouch for those opinions, I've never dealt with Thor) and their prices are certainly on the high side.
I had my adaptor plate made by my local machine shop for £180.
I still had to do a bit of work on it afterwards, and all the measuring and design in the first place, but then I'm using a Mustang T5 which isn't a common swap.
With all the adaptor plate CAD files available from people on here it'd be worth getting a few quotes to have one made.