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

Just curious Kanchi-did you look at my system on my profile page and particularly my Garrard 301? If you prefer noromance’s, my feelings will not be hurt but....
The idler wheel is rubber on steel. http://www.audiosilente.com/garrard-401-idler-wheel-garrard-401.html
"They are a bit expensive and shipping"? Perhaps you mean with shipping. This is no time to be looking to save on things. If you want it done right, you have to pay for shipping. I bought a lot of things from the UK, Ray Clark’s PSU for the Garrard, my plinth from Russ, shipping is not that terribly expensive.
Hell, I got in the car twice and drove six hours each way to pick up my decks from Greg in Nashville. Worth every minute of my time.

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.

@fsonicsmith OMG! that's a beauty. 
I have to admit, I did not know how to look at system. @noromance in his first post had a link to his system and I just clicked. Now I know how to look at someones system!!
Did Greg in Nashville rebuild  rebuild your system?
He is only 5hrs away and I can easily drive.
I actually drove to Washington DC to listen to Greg Beron's system and his tape decks.
I like your suggestion about going all in. 
I will order the Idler wheel.
If I may ask, where do you live?
Thanks!

I bought my Garrard 301 from Greg. Greg says he found it at an estate sale in essentially NOS condition-as if it had barely been used if ever. He cleaned it up and installed an AudioSilente idler and an SMD Acoustics main brass bearing from Peak Hi-Fi at my request. https://www.peakhifi.co.uk/cgi-bin/ecom.cgi?Command=ShowProduct&db_pid=718
Greg does not build plinths and does not particularly enjoy even dealing with plinths. He did recommend the Ray Walker PSU and so I bought one, had it shipped to Greg, and Greg assembled the wiring to make it easy to integrate  https://www.classichifi-shop.co.uk/product/classic-301-401-power-supply-unit-psu/
I kept the old grease bearing since it has virtues of it's own that I may wish to take advantage of someday. 
I then ordered the plinth from Russ Collinson and installed the Garrard chassis into the Russ Collinson plinth and then gilded the lily by adding this beauty  https://www.peakhifi.co.uk/cgi-bin/ecom.cgi?Command=ShowProduct&db_pid=1258

Now on my Thorens TD124, it was entirely different. It had been in my family for 60 years since my dad bought it brand new in 1959. It needed a lot of TLC. Greg stripped it down to the chassis and parts, had the chassis sandblasted and repainted to original cream color and at the time, Greg was able to supply a massive machined aluminum platter and custom bearing of his own design. He supplied the plinth and took all the steps necessary to implement the 12" Reed 3P including having a custom pillar pod machined to raise the arm the necessary height for the thick platter (something rather unique to TD124's where the chassis is elevated over the OEM platter more than usual). It too got a bunch of after-market parts including the AudioSilente idler. Greg's real passion and expertise is with Thorens and the 124. He studied repair of the 124 in Switzerland under one of the former Thorens technicians for several weeks many years ago. 

You are best off shipping your project to Greg and then only going to see  him when the project is done and ready for pick-up. He lives out in the boonies and prefers to meet at neutral locations. I never asked but assume he prefers his privacy and that his house and workshop are exceedingly difficult to find if you are not a local. 

And last, I live in suburb of Columbus OH. If you are ever nearby and want to see/listen, just PM me.