I think you'd be a lot better off doing a bit of research, looking at everything that's available, and building something else.
You're going to be happier with it and it's more than likely going to cost you less.
While I don't have any experience with their microphones, I bought and modified two of their preamps and the engineering varied from okay to extremely poor (in both units), the transformers were "corners cut" versions of the manufacturers' popular models, and a lot of the circuitry was just wrong.
I would have been ahead building from scratch. I like what I've got, but it's WA, so resale value is not there.
Buying used to modify is slightly better, but really, all you're getting is an ugly mic body, a cable and a questionable PSU as the transformer, capsule, and circuitry is wrong.
Seeing what I've seen, I would never consider buying any more of their products.
Anything can be modified;
It's only a question of time and money.
Buying a complete MXL tube mic for the body, cables, PSU and then modding that might be your lowest effort way to go.
I might suggest building a version of Neumann's top of the range (for that time period) M49 instead;
same capsules, Bodies are available from $50-$500, transformers are available from several sources, lots of circuit options.