Welcome to THO. Although your customer has not allowed you the time frame, there is a gob of information on crow and elk gut modifications in those sections of THO to take a look at. Everyone does it a little different, with the Latta Method being the staple go-to.
The taper is morse 2 taper. (MT2, like most mini and midi wood lathes these days).
Check out the Latta Method threads and tutorial, MT2 threads in the crow and elk call sections, and decide for yourself what is your best course of action.
http://thogamecallsforums.com/index.php/board,113.0.htmlYour bit size will end up being 5/8", or 41/64" or 43/64".....which ever you think you get your best results from.
My personal take on your problem. I flat out will not accept an order for that many calls at a time. And I will for SURE not accept an order for more than a single of a type of call I have never built and know will run and hold up to my satisfaction. You have a tall order on your hands.