Barry,
Let's look at this one more time, and I'd promise to try to stay logical and rational:
How do you test the 6072 tube in an M49, when you cannot mount a capsule, because the amp cover contains the capsule mount?
With other words, how do you want to get audio out of this contraption, so you can compare tube functions and sound?
And have you thought about the financial implications of such a modification? What's a new 6.3V. power supply going to cost you, compared to just getting the only tube for which this mic was designed? And what about the depreciation in value for this frankensteined mic? And remind me again, what the purpose for this exercise was supposed to be? To trash a highly collectible vintage mic? No, it was to try to save money, but I submit, the poster will only lose money in the process.
I'd say, what I said before: If you cannot afford an original tube or other vital parts for your vintage mic, and you have start to hemorrhaging value by severely altering it, sell it, and buy a mic whose maintenance you can afford. This may sound hard and cold, but I cannot see any rational reason for proceeding like the poster was considering.
P.S.: another argument against: have you thought of how to heatsink the tube pins of the 6072 when connecting wires to them, and how to mount the tube without socket?