SR20 to S14, so let's go...
 

So I did my share of research and I'm pretty sure nobody did this yet, if someone did, then chime in! I want to take my basic SR20 turbo and step it up from the journal bearing CHRA with the Turbine: T-25, 62 trim 53.8mm 0.64 A/R turbine housing, and the Compressor: T-25, 60 trim 56mm BCI-1.
To the:Black Top S14, which according to my research should use the same turbine, but swap in the Ball bearing CHRA with the Compressor: T-28, 60 trim 60 mm BCI-1 compressor in T-04B housing.

Who know's the part number for this CHRA and Compressor? I want to buy a new or quality remanufactured CHRA and any matching compressor will do. I hope to gain 15-25 whp from this swap...but will I need to change my 460's out for 550's?
Shoot me some info guys!

I still think you're making this harder than it is, but linked is the forum you want to keep on top of... lots of T28's for sale all the time:
Forced Induction Performance Parts - SR20 Forum

just get a gt28 used like sam suggests.

Everytime I've looked for a jb T28 on a Nissan forum, they usually sell for alot.

# Garrett T25 Turbos: Example: Upgrade from a stock T25 wheel to a Big T28 wheel. Prices start at $200

http://www.gpopshop.com/upgrades.html

I just checked that out. This is another one of those times where you take peoples advice and just by a GT turbo ready to go. I'm thinkin the under-rated GT2871. I am running 460's now, so if I upgrade to 550's will they be sufficient? I was told 460's are good to 250hp, what about 550's?

On the other hand, I have a spare SR20 CHRA sitting on my work bench. Maybe I'll have the T28 compressor wheel swapped on it, and get a bigger compressor and see how it runs.

So is this "big T25 wheel" upgrade now considered a T28 (same specs as a T28)?

I think so, I went here: Turbo Upgrades
I bought my turbo rebuild kit from these guys over a year ago, and they were good to do business with, so I think I am gonna send em my spare CHRA and see what happens. I need to find a compressor though, cause I have the standard SR20 T-25, 60 trim 56mm BCI-1 compressor, and I will need to go to a T-28, 60 trim 60 mm BCI-1 compressor.

Gpop's reply:

Thank you for your interest. The T25 compressor wheel is Max flow rated at 250 HP, and the Big T28 wheel is rated at 340HP. So, at max flow the difference is 90HP. On your engine combo we would think that you could gain 15-40HP with the big T28 wheel. Sometimes it is not just the compressor wheel that is the restriction though, you might want to get the turbine wheel upgrade as well and go with the complete Big T28 upgrade. These turbos are rated at 340HP and have been dyno'd on many applications over 300HP. The price for a HP rebuild (a rebuild that does not require any hard parts: comp wheel, turbine shaft/wheel, or bearing housing) and upgrade to Big T28 specs would be $695.00 plus $25 return shipping. The first step in the rebuild is a full inspection. If any of the hard parts are found to be damaged at this point, we would give you a full quote for repairing/replacing parts.

Our turnaround time for standard rebuilds right now is +/-12 business days. If you would like to ship the turbo to us for this service, please enclose your contact information and send it to:

Holy F'n WOW! What a deal! Not. Dude that's a shit load of money to spend just to upgrade that, I think it can be done for WAY cheaper. I do like the estimated HP increase though. I wasn't looking to upgrade the full thing, I was thinking leave the turbine alone, just upgrade the comp wheel. I wonder if I can cut my compressor out the accept the T28 wheel, or if I have to buy a new compressor. The T25 stock size comp is I think 56mm, so the T28 is 60mm, I'd think 4mm on the lathe could be done.

good god thats a lot of money. You can buy a brand new BB turbo for slightly more!

Just by a used 2871. they kick ass on the 240s..

Or just buy a used t28. they are all over nissan forums.