Cart for VPI Scout? Blackbird, Ruby2H, Shelter 901

The 901 is the best of the bunch however you need a arm with good lateral stability and the JMW 9 being a unipivot is not the best match. You could use it on your arm for a while and maybe swap it out for an OL silver Tonearm at some point. That cartridge is so good you might even consider getting a different table for it.
This again depends on your connections and how good a deal you can get.

Curious that you now use a Rega P25 with a modded RB250.
You stated earlier that,

I can't get and deals on the Dynavectors, so those are out.

but you could get a new 901 for the price of a Blackbird.
A Shelter 901 would work well with the modded rega.
So what made you get

I ordered a Dynavector 17d2 and a P-75, so we'll see how that goes.

Color me curious,
Ron