a T3/T4 hybrid will essentially bolt on in place of the stock T3, and if it's internally wastegated you can reuse the exhaust elbow, but will need a new wastegate actuator.
A holset will probably bolt into the manifold (as long as it has a t3 flange), but you'll have to figure out the exhaust (new downpipe), and you'll have to choose between internally wastegated or not.
A T61 is probably a bit too big unless you're building a race car.