Wow, go modern then.
Note that your BB threads were cut with an accuracy appropriate to 1/4" ball bearing races, which can tolerate quite a lot of misalignment. Cartridge BB is fine for you too e.g. Octalink, ISIS.

If fitting a modern external bearing it would pay to go to a shop with a good workshop and get your BB threads aligned and the shell faced to modern standards, or else your bearing life may be disappointing.