I think the best choice is a used Jeep box from a junkyard that you remove yourself. You can see if it leaks, you can feel if it's loose, you can check the code on the sticker yourself. If all that is good buy it. Mine was 20 something bucks. The ratio and effort are perfect.
I would not buy a mexican rebuild from a parts store. Who knows what you might get.
you feel you can judge the condition and IF
you can find one, the used Jeep box will probably be the lowest cost deal.. From my experience, you can't easily determine the condition unless the engine is running with the wheels on the ground, but that usually not the case in a wrecking yard... For my next "low budget" project, I may try to find a used Jeep box, but already knowing it won't be as firm as I have become accustomed to with the AGR... But I also worry, because the "newest" Jeep box is nearly 20 years old... My guess is that most are probably already worn and loose...
As for the rest, a lot depends on your budget... Generally the better options (Lee, etc) are going to cost the most money, while a parts-store rebuild can be significantly less expensive but more likely to be out of spec... In the middle is going to be something like the AGR, with known specs.
There have been some "rebuilders" listed that do custom rebuilds...
Personally, I have installed several AGRs, and never had an issue, and great customer service when asking questions directly with AGR. Aside from those members here, I don't know anyone that has had problems with them... I LOVE the firmer feel of the steering with the AGR box (even firmer than the Jeep box), not not so stiff that its still easy to turn the wheel.
As for pumps, I have used "original or parts-store rebuild pumps, and never had an issue with performance... I guess IF you need a new pump, then the extra for a custom built pump may be worth it, but if you are just replacing a wornout stock box, not sure the custom pump is worth the extra expense...