Thanks Viking 85: the specifics in the scenario may allow for an estimate to be made of production needs:
according to an internet source - group centre needed 13,000 tons a day on the offensive . That figure is from the plan I think, not the actual amount delivered...
To spare your agony, doing the obvious scale up and subtract this, add that, apply fudge factors ,,.for an attack force of 7 million men - it comes to about 70,000 tons a day of production averaged over the year (which I know will be wrong, but I tried). Just for operations.
To replace the 'scorched earth' infrastructure you may need a lot more (Rail, ties, signals,,,,,,, or road levelling ballast, diggers.. in any case bridging materials.....) if you want a 300 mile advance per year that would be approximately 2 million tons more. Plus the replacement rate of the motor pool and stock, plus tools, motor parts, fuel for the transports.... another 3million perhaps
So the production for immediate war work is : very approximately, 30milion tons per year as a planned amount for a force of 7 million men - cut to size for the force you envisage.
With a GDP of 900million dollars equivalent to pay for it.... 30$ a ton, hmmm... Can Hitler afford to invade?