I second Jac Mac's suggestion--there is NO good reason to run a 351C. Besides the fact that the GT40 originally came with a 289/302, the simple fact is that the 351C isn't a very good engine (which sounds sacrilegious from a lifelong Pantera guy, but it's quite true). Add to that the fact that you already have a 289/302 right there in your hands, and it becomes a no-brainer.
Have the gearbox converted to GT40 orientation, get yourself a GT40 bellhousing, and away you go.
You will need to think about final drive options--driveshafts or CV-joint shafts? Although there are adapters available to let you bolt a CV joint to the stock Pantera output flange, if you're having the gearbox rebuilt AND you plan to use CV joint shafts, you can kill two birds with one stone and have the output on the ZF changed to CV-joint style, as used on the BMW M1.
It just shows that you need to think the whole plan through from stem to stern before you start spending any more money--and then plan on spending a LOT of money no matter what you do!
