hi tom
i have a 4 speed box, the gears are a little worn but it's usable. i also have the output gear that fits into the diff. you will also need the dished flange as well but i don't have one i'm afraid.
i tow my dingo on a 3 axle trailer and have done hundreds of miles with no problems. it's also under the weight limit of 3.5t just make sure the towing vehicle is rated to pull and that the tow bar is as well
type "throat mic" on ebay and you'll get thousands of hits. it might be easier and cheaper to get a motorbike intercom kit and fit it inside whatever headset you want
about 5m away from the pit entrance is a hump in the path, there's a piece of churchill track sticking up from the ground. i have a feeling the hump is made up from bits of tank that was bulldozed out of way during a clean up.
don't build a replica a13, if you want to get stuck into something early then how about an a9. i know of a wreck that is recoverable. much better to do a resto than a replica