hey sarge, not too sure if i can help you, but when i purchased my FC it had a 186 with 5 speed already installed, there are bellhousings to suit available from CRS and Dellow Automotive (as installed in mine). a new trans tunnel was fabricated and im not too sure what the tailshaft is from but its beefy. ( could have been cut down HQ???)
but while ive got you, ive also got a disc rear out of a VN and was wondering how you adapted the handbrake cable.? did you switch it to floor mount?
mine is still in original position under dash as i have bench seat still, but cant get the rear cable to meet with the cable from the handbrake. i was told an EH intermitdent cable might match the two up?
sorry wasnt much help with the box but feel free to ask and i may be able to help you out.
good luck
dean