Good choice for bhw turbo upgrade?

I found many turbos on ebay but I'm not sure which ones are suitable for my car. GT2256V, GTA2056GVK, GT2056V, BV43A, BV43B. I'm not sure about the differences between GVK and G or B and A etc. If anyone could enlighten me I would appreciate it. I have a b5.5 bsd, 5sp, tdtuning stage 2, Colt stage 3 ready to drop in when I install a new turbo.

First Question - Have you used the search function? Not being a smart ass, this question has been asked a large number of times. With search you will find those older answers.

Next suggestion, since you have a TDTuning tune, why not ask Mike? He has a ton of great experience and knowledge

Do you have a clutch that can handle it?

Mild upgrade is a BV43A - from a PD170 longitudinal setup. BMN engine code I think

Others are a lot more work.