Once you put an injector at each port, even fuel distribution is easy. If for some stupid reason the manifold was run wet, all bets are off.

I guess maybe I need to clarify my intentions.
I want this to be as reliable as stock, but would like it to be able to reach a sustained 65-70mph for say an hour or so when needed, highway driving. It will spend most of its time in the 45-55 mph and under range. I was hoping to do this with a few upgrades and bolt ons, possibly a slight bore, but not a ton of machine work. I'm not looking for serious gains like a Turbo swap would give. I'm a jeep guy and have zero experience with these, I have no baseline to go from as I have no clue what a "fresh" Raider 2.6 is capable of MPH wise.

What I would do:

Stock, The bottom end is really good.

The only gotcha is the balance shaft chain. When people ran these motors with it loose / out of adjustment it would slap. Over time that could cause the pivot to fail.

The fix? A TSB on the pivot bolt for torque and keep the chain tensioned. Do that and your good to go.

If you run balance shaft, the clevite 1805M bearing kit is the best. The large bearing eliminates the parting line.

Compression Ratio: A slight gain helps, but the main thing is to not end up with less than stock. This is a very common issue, most aftermarket pistons are decked.

Crankshaft: Stock is fine, a hardened turbo crank is a bit more forgiving. I have beat the snot out of the stock unhardened unit on NA motors. When I built my last motor I had a NA crank Ion Nitrided, it worked really really well.

Bearings: For a carb motor there are no bad choices. ACL Aluminum or Clevites tri metals have both worked well for me.

Check the blocks deck for cracks around the exhaust bolts.

A factory style aluminum oil pump is a good choice, I never like that aftermarket cast iron pumps.

I like coated piston skirts... All my motos get them. Performance coatings does a good job. web page

I only coat the skirts. I never found any improvement with the coating on the piston tops, but it might give you a ting boost in CR.

A good machine for block prep is a must.

Resize the rod ends and get the crank checked.

That gets you a decent short block to build from. Any piston ring thats not a plain cast iron of a fancy TS gapless will work well. Factory was chrome, and works very well. Moly is a good option but harder to find.

What carburetor would you run with that scenario?

If you want sustained highway speeds, its not just the motor you need to look at.

I had 33s and running a weber. It would hold 80mph just fine for long trips. Only problem were steep highway climbs. So I did the turbo swap and have 4.875s waiting to go in.

What tires and gearing you run can play a big role in highway speeds.

The truck is completely stock, with a 1" body lift and 31/10.5/15 Kumho M/Ts on factory steelies. If I can maintain at least 65mph reliably I'd be happy. When I got it, it was meant for a parts buggy, but it's way too nice. Had a bad head or gasket,I didn't even check which. Just ordered a new NJV one. It ran mint. But 50-55mph topped it out and it struggled, it was tired. Ive never been in one, so I didn't know if maybe that's just the way they were performance wise, Suzuki Samurai-ish. I love the things,they grow on me daily, a nice break from the jeep scene. But I really want it to be a little more practical, mph wise.

Sounds like a leakdown test and a compression test are in order. I ran 60+ pulling another Raider from Orlando to Jacksonville. The only thing done to that motor was a rebuilt stock Mikuni.

Hmmm. I think you have flying saucer problems.

The carb secondary barrel is vacuum operated, and if the flying saucer on the carb, pside mounted at an angle with a single vac hose, has a broken diaphragm, and when that happens, the truck is a REAL dog, and not just doggish, and will pull ok up to about 40 and then fall on it's face due to not enough air.

To test the thingy (mitsu calls it a "depression chamber") pull the vac hose from the carb end and apply vac to the thingy, and then open the throttle manually and you should see the secondary barrel (the pside one) open up. If the thingy won't hold vac, it's dead and you need a new one. When doing the test, have the engine warmed up so the choke is open and out of the way, and remove the air cleaner for access and view.