The idea of spending good money on a set of Realistic Mach 1's today seems silly! The surrounds are going to be rotted the voice coils are probably not prsitine 50 years latter, the cones are likely not that great either. You have caps in the cross over's that likely need to be replaced etc....Everything old is not that great and also most things 40+ years old need a lot of repairs to make them fully functional. Speakers are just as much mechanical as electrical.
People romantisize speakers for some reasons. Paper and foam and rubber does not age that well. In fact transistors adn resistors age much better than paper, foam and rubber do. Even if the speakers are NOS or NOB a 40 year old speaker is still a 40 year old speaker. I can see wanting to keep the enclosure though since some of these old enclousers especicaly on truly high end stuff is often a work of art!!
When I am bidding on old gear on ebay for example no matter how nice something might look I always keep in mind that a lot of gear will need to have new capacitors, sold solder joint repairs and an alignment at the minimum. If you do not keep that sort of thing in mind you end up over paying for something that while never used is still old and degraded. By the time you add in the cost of parts and an alignment you could have bought modern gear of equal or better quality that needed nothing.
I own 6 different 2 way radio's that are either NOS/NIB or close to it. I am recapping all of them because the youngest one is from 1998 and oldest one is from 1966. I will have to send them out one at a time though for an alignment. People over pay all the time on Ebay because they either do not think this far ahead, are ignorant to how cosmetics mean nothing to time with regard to capacitors and such or they just had to have an item no matter the cost and allow themselves to over bid.
So guys keep in mind old gear even if it has never been used likely will need work if you want it to sound like it did when new. The worst thing you can do to electronics is not use them that shortens their life more than useing them does! Using a piece of gear with dry old caps in it is a recipe for disaster because often IC's and discrete devices not made any more will be taken out by a failing $0,10 capacitors or $0.03 carbon resistor.
Do not let romantics cost you money chasing after a sound that will never live again becasue no one makes them like the used too. It is not enough to own old gear the gear has to be electronicaly and sonicly as it was when it was first built 30, 40, 50 years ago and that is impossible to do.
Instead chase after a sound not how the sound was produced or the brand of gear used at that point in history to produce that sound. No matter what you do purist will never accept any substitutes and will always insist the new thing is not as good and the young up and coming generation will not be able to afford your gear. As usual the old fat men with money will get the all the toys and the people in the middle will be the ones hunting down vintage gear and restoring it with modern parts attempting to capture what once was.