For what its worth, I think I should point out that nearly every turbo listed here (I may have missed one) will need to be used in pairs for our 5.0s and maybe even on some 3.8 V6 Fords. I'll attempt to somewhat narrow down the theory behind picking a/two JY Turbo(s). I will try and get a list of JY single turbos that you can use for those interested.
The general rule of thumb is to get a pair of turbos that were on an engine thats roughly half the size of yours. Since we've got 5.0's, that would suggest a pair from a 2.5L engine. This doesnt always hold true, as different goals and turbos will create different powerbands. Some turbos came from the factory with different applications, or shall we say the factory had a different goal for the particular turbo/vehicle combination.
Take the Ford 2.3T engine, produced for many years in many different configurations. Most 5.0 guys would want to use the '85-'86 Garret T3's with .60/.68 turbine and compressor A/R ratios, respectively. The Ford T3s also come in .48/.60 and .43/.48 configurations (kinda late right now so I may have gotten the numbers wrong). The smaller A/R ratios will reduce spool up time but will also reduce top end airflow. The .60/.68 turbos will probably see full boost by about 2800RPM and make power all the way up to 5000-5200 RPM depending on combination. For the most part, they'll run out of steam by about 5200-5300 RPM at most. The smallest of the Ford T3s will run out of steam by about 4600RPM but will probably come on around 2000 RPM. Now, you can't go out and pick the biggest A/R ratio because you have to find something that will compliment your power band. Go too big, and you'll increase turbo lag and may not even make useable power. Go too small and you'll blow the tires off and fall flat on your face when it comes time to shift.

To come to the ever important question: Which Turbo(s) Should I Use?????
If you are going to ask a question like this, make sure you have asked yourself the following:
What are my eventual HP goals for the car?
What is my intention, weekend warrior/drag car/daily driver/street strip car?
What is my budget?
What are my do it yourself skills?

Cheap, reliable, and fast..... pick two of the three. You can build a budget conscious single or twin turbo setup. For the most part, you should be able to see the same fuel mileage as when your car was bone stock. Most guys will want more. A pair of T3s on a bone stock 302 will nearly take you to the power limits of the stock block. You can easily make 350hp-500HP with a pair of JY T3s. Just plan it out and THEN start buying parts. Ask and re-ask the same questions. Do your research until you're comfortable. If you're like me, you like doing things yourself. I researched for a year and change before I started to build my JY turbo kit. I got lucky with all the parts and whatnot, as I scrounged hardcore for the ultimate in low buckery. All in all, I put in a week and a half STRAIGHT with several all nighters in between and about $1300 in parts. If you're building your own setup, expect to pay more around $2000 for everything as long as you have the tools. I was very lucky to have access to the tools and people that I have around me. It's a lot of work, but the first time you hear that blow off go PSSST it's all worth it! Then the first time you roast the tires from 1st thru 3rd gears it becomes evident it was more worth it than you initially thought. I have forever caught the turbo bug. The next time out, I will take even more time and make sure I have the right injection and whatnot to make sure I can command all the EFI parameters of the car. Otherwise it has been fun beating up on Porsche's, DSM's, Mustangs, Z06, Turbo Type R, 350Z/G35 Coupes, Camaro's and even a GT500.
SS