I called several guys dropping axles. Most of them said they never done one, but it could probably be done. But they would not want to guarantee the outcome. Meaning, you lose your nice core and pay for the drop, no matter what it looks like. Hard to do with a hollow oval tube axle. Much easier to do an I-beam.
I believe the John Mummert 27 AMBR [ about 10 years ago. ] with a V-8 60 engine had a dropped Ford tube axle. . Someone here might have a picture.