I wouldn't do that. The T56 isn't strong enough to handle all that torque. You're much better off with a Tremec TKO.
The conversion to a modern
trans is notall that difficult, but not exactly cheap, either. The old style uses a push type clutch, with a clutch lever. Modern clutches are pull type. Fortunatly, there are conversion kits available.
You could also go with a hydraulic clutch; either a slave cylider or hydraulic bearing.
Matching up the bellhousing can sometimes be a problem. T-5's were designed for the small block crowd. Fortunatly, there are some aftermarket companies that can help you out.
I'd contact Mustangs Plus. I'll bet they've done a bunch of these swaps.