Doug C kindly has been helping me with the measurements on this adapter and confirmed my understanding of the required bushing
The problem is that the Econoline 6 cylinder block is internally threaded so an adapter is not required
What Doug has seems similar to that posted by 66Tiger289 but the PO has ground down the end protruding into the Econoline adapter for clearance. See pic following If you need the block bit this is one way
While this would work fine, I am going to machine a small block specific bushing per the very crude working sketch attached. Note the mix of SI and Imperial measurements!
Either machine your own, buy the Ford part and grind it down, or let me know now if you want me to machine one and post it to you. My offer is a one time deal as this is a hobby. No idea of cost until I do it, but machine work here in Thailand is about 30.00 hour + materials and this is a hobby and not a profit centre.