Best Tonearm and Cartridge for 4K or under for restored Garrard 301

Just for the record, what I wrote and what I had in mind have nothing to do with tonearm length.  The same rules apply no matter what the length, and I was not meaning to advocate for 9-inch tonearms.

Chakster, on the issue of graphite vs slate, I do owe you an apology if you were talking about mats in the first place and not plinths.  The OP was asking about plinths, and I assumed you were referring to plinths made by OMA, which are, or were last time I looked, of slate, not graphite.  On the other hand, if you were discussing platter mats in the first place, mea culpa.
I'm also sorry, but your argument about the effect of a high mass counterweight is specific to FR and Ikeda, and I am talking in general about the calculation of tonearm effective mass.  A heavy CW, which because of its weight can be placed close to the pivot, can have the effect of reducing effective mass, because the factor of distance between the center of mass and the pivot is squared, whereas CW mass is to the first power.  Those are facts. Ikeda didn't abrogate physical laws.  If you want to minimize effective mass, you are best off with a heavy CW that can be placed as close as possible to the pivot vs a lighter CW that has to be further from the pivot to achieve balance or the desired VTF.  That's all I was saying.

Chakster wrote that Oswald Mills Audio plinth is made of graphite. That is incorrect. They are made of Pennsylvania slate. Slate and graphite are two different things.
Also, perhaps paradoxically, use of a heavier counterweight could have the effect of reducing the effective mass of the tonearm overall. This is because the effect of the counter weight on tonearm effective mass is proportional to its distance from the pivot-squared, times the weight of the CW. Thus the distance from the pivot is dominant. And substituting a heavy CW for a light one will bring the CW closer to the pivot, all other things being equal.

I agree in principle with what Miller carbon says about having a direct connection from the cartridge all the way to the input of the phono stage, but that is only an ideal goal and certainly not a necessity. I do insist upon it with very low output moving coil cartridges, but I cannot hear a difference with higher output moving magnet cartridges, for example.

kanchi, I think OMA was known and is known for slate plinths, not granite. Many of the cognoscenti who have tried granite (I have not) were underwhelmed and preferred slate.  Furthermore, there is a wonderful low production turntable based on the Lenco idea (the Saskia) that is entirely made of slate and very well regarded at the high end.

The "beauty" of a medium mass tonearm is that you can easily add mass, if you decide to go with a very low compliance MC cartridge.  Whereas, medium mass tonearms, as is, mate well with most medium and medium high compliance cartridges.  On the other hand, you cannot easily reduce tonearm effective mass, if you should want to try a very high compliance MM or MI cartridge from days of yore on a very high mass tonearm.  So, I would stick with medium effective mass and think about Triplanar and Reed, primarily, if I were you.  I've never heard the Kuzma, so cannot exlude or include that one. fsonicsmith says his Cocobolo-armed Reed is "medium" mass at 18-19g.  I'd want to stay in the 11 to 16g range for max flexibility.  I use a Reed 2A with a Red Cedar arm wand.  Red cedar is a little less dense than cocobolo.  But rules like this can be gently broken, because if you look at the equation for resonant frequency, you can see that there is quite a bit of flexibility in values for effective mass and/or cartridge compliance allowed, while still staying in the desired resonant frequency range of 8-12Hx. 

As to slate as a plinth material, it's been excellent for me.  I own two turntables with solid slate plinths: Lenco L75 and Denon DP80.  They're both quite neutral sounding.  Slate is in and of itself "constrained layer damped", because that is the nature of slate per se; viewed from the side there are overlapping irregular layers of material, which is what makes it very difficult to cut with a water jet. (I know this first hand.)  On my Technics SP10 Mk3, I used a more massive piece of slate coupled to a cherrywood base, mounted to the slate from below.  I listened to the Mk3 before vs after I attached the wood base, and I heard maybe a 5% uptick in solidity and neutrality with the wood.