Turbo and intercooler

[Zoupop]

Hi,
Im thinking to change my stock turbo for a GSP t3/t4 ebay turbo and an intercooler(26x11x3) setup with 2.5'' piping but I don't know if the size are ok or to big.

Here is the spec of that turbo :

Intake: 3''
Inlet: 2''
Compressor trim: .50
Compressor Wheel diameter: 50.16 / 76.84
Turbine Wheel diameter: 54.06 / 65.20
Exhaust Trim: .57ar

What is the trim means and is this to much?? Is the T3 flange got standard size or you can have T3 bigger than other?? Can I use an external wastegate??

thanks, all comments are appreciate and sorry for my English (im from quebec)