Hey mate, I believe you would need to buy a wrecked BF with a ZF as you are right about needing the wiring. The tailshaft would also be different, which id take the one from the donor car to get beefed up.
It may be easier buying a sweet BF and transferring your goodies onto it if you aren't too attached to your BA.
In regards to having it fully manualised, haven't heard of this. just get the box beefed up by a reputable builder (will depend what state you are in) and have it tuned properly. Then run it in manual mode like @discostig who preaches the manual mode lyf