If it were me, a D60 with 40 or 44-spline axles & a spool, driven CAREFULLY with a well built PG (Rossler, TCS, Brunos, etc.) budgeting 5500-10k for a trans would be what I'd expect to pay for a driveline. Keep in mind, though that early F/Cs ran TFs & D60s & were making the kind of horsepower, and more, you're talking about & they lived pretty well. The top SS/AH guys are running in the 900hp area & they're just using a built TF, so I think you're over-building & over thinking your project.
For what it's worth, Car CRaft Magizine's old M/P car run by then-editor John Dianna had a D70 in it, so I guess it IS do-ablebut with today's engineering technology, cryogenics for examle, why would you adhere to the old "bigger is better" theory?