Excuse my age, but a 1973 P-bass doesn't resonate with me as a "classic", just an old bass. In fact I have owned mine since 1975 when I bought it "used".
At that time I was a hard working, girl gettin', boho musician
. The guitar had to be able to keep with with the nightly abuse. I realized that it was simply a tool for me, nothing more. There were a few changes that needed to be made.
1) The pots were crap. Sorry, you classic pot lovers, they were crap. I replaced them with high-end sealed pots that to this day are smooth and quiet.
2) The bridge sucked. It was functional, but a BadAss II would add far more sustain the the guitar. Done.
3) That plastic pickguard never had a chance. I busted several by ripping the cord out of the guitar while running off stage. I didn't mean to be so abusive, it's just that - you know - that chick with no undies that kept lifting her skirt at me all night was ready and I wanted that guitar out of my hands in a hurry sometimes! Like I said, this had to be a working mans axe that could handle reality. So I replaced the pickguard with a brushed metal one that wouldn't break.
To this day I still know that these were improvements to the original stock '73 p-bass. I'm sure the value of the guitar today is diminished as a collectors item, but are those buyers ever going to play those old guitars out on a real working gig? -h