Ray,
Don't take this the wrong way mate, BUT if it were me i'd fit it with the .63 housing bud, the difference in LAG as people call it will hardly be noticable from the .55 and you'll be abit more top-end too on the .63, best move i made mate....

remeber i've just come form the exact same Turbo as you, you'll gain near on 70-80bhp with the T34.63 from the T3...
Edited to say,
What chip/Injectors are you running now mate??