at this stage in the game, if you're not going to upgrade to an ms3 based system, there is no actual reason to run a v3 or 3.57 over a microsquirt regardless of whatever axe rick has to grind against it. They run the exact same firmware, you don't have to figure out any bull**** little circuits to run wasted spark (or cop on a 4 cylinder), there's nothing to goof up soldering up a board, and it's cheaper.
the reality is almost no one bothers to go beyond what a microsquirt offers (that an ms2 v3.0 will have), most either go straight ms3-x (Which will require re-wiring the car), or more often, one of the ms3-pro offerings if you need something like that. Or not megasquirt at all.
The rex stuff is likely supported, an lh 2.2 distributor could be dropped in to cover things for a basic setup, or (my personal preference back in the day) the lh 2.4 60-2 flywheel/flexplate/sensor/bracket and run wasted spark or wasted coil on plug.
the rest is fairly straight forward, putting together an adapter harness would likely be along the same lines as the plug and play 2.4 stuff, though not entirely (and bonus, you already have a map sensor and air temp sensor under the hood, so two less things to buy) identical. TPS is nice but not required.