I've always taken that lore of them being prone to blow up with a grain of salt. The dead aren't here to rebuttal but here's my take...
All that talk is perpetuated by one guy. Since he was considered the Marshall Major expert, everyone just repeated the same sentiment with nothing but his word to back it up. This comes from the same school of thought that you have to bias your tubes extremely hot to get a good tone. If they were popping them it's because they were running them in extreme conditions. The ultra-linear power amp isn't unique and while the Major is the only Marshall design with a UL power amp, Fender, Ampeg and countless others have thousands upon thousands of these in circulation and they're not blowing up.
Bottom line, they're not gonna blow up just because you put an overdrive in front of them.
I've got two '73 Major Lead 1967 amps. You can certainly cascade the preamp and add a master volume which will negate the need to dime the amp for a nice overdrive. The UL taps can be disconnected with some modifications although the more you tinker with it, the less it's a Major.
What is it that you're looking at? It's not very cost effective to build a Major replica at the full 200W. The replacement transformers cost wayyy too much. Any 200W guitar amplifier is kind of a gimmick anyway. I had a Thunderverb here at the shop for a while and if you played through it not knowing it was 200W you wouldn't think it was any louder than a typical 100W amp. That being said, if it's a 100W amp with a UL power section you can certainly run it with an attenuator and not need to modify it to make it useable at lower volumes.
I did go down the rabbit hole with the Blackmore/Major connection a while back. There was a plethora of different mods they went though... extra gain stages, cascaded preamps... They even added more power tubes to one of them!!! It's nuts.
