The unit is super clean but clearly needs work that I would prefer to leave to the pros.
Please see my profile and system for confirmation that I have experience with restoration of the 301. My recommendation is to send the 301 to Greg Metz of STS/Classic Thorens just outside of Nashville for meticulous restoration. Greg is a perfectionist. His prices are just a tad on the high side but you get what you pay for.
Now this is going to perhaps offend you or some others but without knowing what you do for a living and/or what your financial responsibilities are, it is a complete shame, imho, to limit the potential of a "super clean" 301 with your budget. $4500 is a much more reasonable budget. Wait, save, re-allocate, do whatever you need to do but restore the 301 with an adequate budget for restoration, tonearm, and plinth. Please :-).
Also, someone above mentioned that there is a school of thought that super-dense plinths such as slate deaden the sound. I agree. The sound with a slate plinth and top end tonearm and cartridge will sound more precise but sterile. The liveliness is gone. But on the other hand the 301 has a somewhat noisy motor/idler drive such that a mid-weight plinth with good footers will help. So don’t expect perfection and instead accept the inherent compromises. I happen to have one of the Muldovian plinths linked above just sitting around collecting dust. PM me and if you want it, you can have it at a price that will be bound to make you happy. But-I warn you in advance-while it looks very nice and seems to be built well-it is still rather cheaply made.
And last, while there are tons of great tonearm choices out there and no single best-for-the-money choice, you might add these to your consideration; https://purefidelity.ca/product-category/tonearms/