Tonearm suggestion for Garrard 301 schedule ll oil bearing?

IMO from point of effective mass
Groove master II
or SME 3012 but R version or early versions with stainless steel tube.

There are a lot of reviews on the 3012 I, II, R. I've always uses SMEs on Garrards, and Thoren TD124s. I currently use a modded 3012 II, a 3009 II (detachable HS), Jelco SA-750L (10") and SA-750E(12").

The 10" is on a Russco (Shure V). My MM rig. (I pick them up every now and then) I call um Garrard Killers. They are, David vs Goliath. Russco, GRK, and Sparta. About twice as heavy and twice the size..BUT direct rim drives like the Garrards, unlike the Thoren, TD124s

The TD 124s I use Dennon 110, 103 and 103R. I'm waiting on a valve phono/ RtR stage (Decware).  I currently use a C20 Mac and C2500 both with good sounding phono sections. C20 was modded for MC use, quite good.

I know nothing about the Grove Master.

SMEs and Jelcos, BOTH are good tone arms and plenty of parts for the SMEs. I haven't used the Jelcos enough to see any wear issues.. Good tonearms, though. In use for 3 years, now.. The SMEs 25 and 35 years I know of.. I rewired one and added RCAs to both..

Regards

The Groovemaster is fantastic. I use them (and caveat - I sell them too). I would say the arm is quite neutral, meaning won't 'add' warmth etc.
For heavy / low compliance carts its about as good as it gets in the price range.
Btw the SME 3012 series 1 ( original 1950's) is quite a bit higher in effective mass compared to the newer 3012R. There are tons of fans for the R though.