Just bought a t-3 with a/r's of.42 turbine side and .48 compressor side is this good for a zc if not what would be the best? thanks

 

that should be ok, but you might want to go bigger later on.

 

The .42 compressor housings are just that... .42 AR. The compressor wheel itself is actually .50 trim, good for 250-ish.

Sounds like about all you care to push on stock D16 bottom end. I'd go higher, but only for short spurts and I'd be expecting it to die.