Is this going to be a streetbike or a drag-race only bike?
For street I wouldn't go bigger than a GT28,if it's race only,then you have more choices but remember the bigger you go,the more lag you'll have.
The log-style eBay manifolds are junk,don't even waste your money on one. Nobody really makes turbo kits for the 1000's any more in the USA,so you'll have to beg Richard at RCC Turbo's to fab up a manifold for you or try BigCC in England. Or,if you have the skills fab your own,however if the manifold/turbo sits too low(center line of turbo below cl of crankshaft) you'll need to add a scavenge pump or it will be a crop-duster(burning oil and large clouds of smoke out the exhaust). Same goes for the plenum,you'll have to see if BigCC or RCC will make you one if you can't fab up your own. Again,avoid ANYTHING SOLD ON eBay thats made in China for your turbo build.
That being said: avoid doing business with Jason from RPM Cycle/Velocity Racing
,they used to
be on top of their game with turbo kits/parts. Not anymore. You've been warned...
The most popular GSXR 1K's to boost are K1-K8,anything after that you're basically on your own trying to fab something up as they aren't too popular for serious modding/drag racing.
After building two turbo bikes,the best advice I can give is to spend the extra money on the best aftermarket engine internals you can buy. Build a purpose built,low-compression turbo specific engine. Bolting a turbo onto a stock engine is a very expensive time bomb ticking away.
I was given that advice by more than one old-timer and I'll pass it along to you. Cut corners on a turbo build&you'll end up hating your bike very quickly.