Be wary of less standard bottom bracket shells on some older frames
This really isn’t the problem it used to be. In the last few years, companies have offered inexpensive square-taper and Hollowtech II bottom brackets for Italian, French, and Swiss threading.
Right now is a great time to be fixing up an obsolete frame, and stocking up on spare parts.
I like to make fun of that argument in my use of metric. I’m 19dm tall. Salt Lake City is about 1Mm away. Often throws native users off kilter a bit.