Your asking far to many questions to be building your own turbo setup, especially if your trying to do it under a grand. Unless you know a really good machinist that is family, you aren't goign to be making anything for a custom turbo cheap.
I know that fuel is in short supply as well. I'm goign to start with injectors. I beleive stock to be around 200 CC/sec. well That's all nice and fine but 400's are not enough for a 14b at 16 psi. Keep that in mind. Now that you ahve bigger injectors say hello to an expensive fuel controller. (that you have to tune.) Now that that is done, you need an exhaust.
Turbo flanges:
The mitusbishi flange is pretty much the same all the way from a t-25 a 20G. Please keep in mind that the t-25 (found on a DSM) is a garret turbo fitted with a mitsu flange.
Which turbo to get:
Well the turbo to get depends on what's been done to the bottom of your engine. WHat compresion are you running, how much flow can the cylinder head move, etc. If you have a head that can flow 500cfm a minute, and you slap a turbo that can do 600, your almost waisitng your money until the head gets ported. Also think aobut how much can my stock bottom end take, if you buy a 16G (which I've personally seen put down 400 hp on a dyno several times,) And put it on your stock bottom end, and then you tune it to say 12 psi, and takes a while to spool, then takes off liek a rocket, your bottom end seems fine and you turn up the boost, look for holes in your pistons.
If you free rev the engine before its warped, it isn't uncommon to find oval shaped cylinders. You have to wait before you turn the car off so that the turbo can coo down, (throw money into a turbo timer that problem is solved.) you have to reprogram your ecm around a turbo system no-one has to utilize the full power your car is capable of producing. (big $$$$)
I think that you need to read much more, and reconsider what your doing. I had the option to jerry-rig a turbo on my integra, and i wouldn't do it, hell I bought another car that came turboed. I don't like to see 1 second wonders. To build power properly you have to know what your doing, or payto have it done. If your trying to be cheap, it won't happen. I've been in the 13's in a turbo car for less then a grand in upgrades, (my first eclipse,) And if I hadn't been rear ended i really don't the car would've lasted long. Learn from my mistakes at least. I dont' liek to see cars get destroyed especially when it comes to a nice car.