Looking for suggestions for either having my stock manual steering box rebuilt for my Dart, or purchasing a new unit if available.
What have you guys done?

I don't think "new" exists, they will all be "remanufactured" using used parts from cores. More than likely everything in yours is still good and if anything it probably only needs an adjustment. A rebuild is also easily accomplished on your workbench.

One thing to note, if your Dart is or was a 6 cylinder car the box will have a bushing in the steering shaft instead of a bearing and this should be swapped for a bearing which requires a different case or complicated machine work.

Too much steering wheel play I am assuming. I would locate the shop manual adjustment procedure which involves the top slotted bolt and the large ring nut (I forget the proper name for it) on the rear side & see if that procedure fixes you up.

New would probably only exist in the form of the Flaming River (possibly others too) box.

While I agree with the comments above about adjusting or rebuilding, it might be good opportunity to swap up for a quick ratio 16:1 box if you don't have one already.

Lares has both new and remanufactured non-power steering boxes in both 24:1 and 16:1 flavors. New is only slightly higher than reman, but with the reman 16:1 unit there is a $150 core charge!

R.

Flaming River stuff is built near Cleveland. They took their name from the widely-reported news item, when the river caught fire. That's right, there was so much pollution that the river was flaming.
A little pricey but built in USA and it all looks good.

Lares has two remanufactured boxes and two new boxes. 24:1 or 16:1 non power assist. Rock Auto will ship the new 16:1 box for around $300. The remanufactured 16:1 box costs nearly the same as the new one, and has a $150 core charge. I think they're built in Minnesota.

R.

The Flaming River Mopar manual box is built in Argentina. Mancini Racing sells a 16 to 1 manual rebuilt box as well..

Just my $0.02...

Firm Feel has all the parts you need to rebuild it yourself.

It's actually pretty simple.

Bullseye...

As needed (1) adj your current one (2) rebuild your current one (3) $300 for a new 16:1 ain't too bad & there was some good threads on if the steering input was acceptable on the street, alot had to do with tire/rim size. when we went to a 16:1 on the A body stock car it was a night and day great improvement difference in the corners, before (with the 24:1) it was a hand over hand discombobulation to turn. they are pretty trouble free, I would for sure adj it correctly & see if it turns smoothly by hand lock to lock then install it & if good on your bench then highly likely its all good.

A 16:1 box takes 30% more effort to turn - simple math. This can mean the difference between one hand steering and two hands. Two hands is arguably safer BUT who always has two hands on the wheel !! Just some things to consider.

First choice should be rebuilding. Unless worn, the factory parts are almost always better than the replacement parts. Yes, aftermarket 20:1 and 16:1 worm gears have been made and their quality has varied. Anyway, the question wasn't about changing ratios, it was about rebuild. It may just need repacking with fresh grease and new gaskets, readjust and good to go.

And at speed it's almost irrelevant.

Trying to parallel park, yeah you'll feel it but pretty anything above a walking speed and you won't notice.

E bay has plenty of new Manual boxes, both 24:1 and 16:1, aluminum. I just bought one, but haven't had a chance to give it a going over. I have a box that I rebuilt, but the MP 20:1 gear is crap, so I figured I'd be a Guinea Pig.

This is interesting:

http://www.ebay.com/itm/1966-to-1979-Mopar-Dodge-A-B-C-E-Body-Car-Truck-Manual-Steering-Box-Gear-Box-/361882567453?hash=item5441e1c31d:g:~PoAAOSwImRYfksk&vxp=mtr

Lighter and stronger than a stock unit? Anyone know of these? $217 isn't bad if it's as it says.

Correcto..
Parallel parking requires significant muscle effort but...
Also also if one is running radial tires this too requires more muscle as well...

Just my $0.02...

And what requires even more effort is a power steering setup with no power, did that for a couple years in my 64 300, with fat radials up front too.

I lived.

It's kind of like the .45 kicks myth. It kicks in the hands of those who have never fired one and fast ratio steering is hard in the hands of those who have never had it.