The guy who I dealt with didn't have a clue what I was on about but said he would do some research and ring me back. Sure enough a few hours later he did. Turns out that the Parts Manger know all about the 4g54 in the B2600s, they call it the 'AM' motor. Anyway he said that Japan was out of stock but if I wanted one they would make another run if I went in and paid up front.
So thats what I did
It was $373nz plus GST, not trade price but cause I work in a car yard he did give me a good discount. It should arrive in 3 weeks time.
The part number is, for any one who wants to order one, MAM0216210B.
Im not going to use the RX7 box but a box out of a Ford Courier. Its the same as the B2600 unit. Better ratios than the RX7 box and the shifter position (which most of you will know) is near on perfect.