i wouldnt go t3 turbo if hes worried about lag, unless of course its got a roller bearing core

there are things you could do to reduce lag - get your manifold and turbo heat wrapped, maybe a lighter flywheel could help to im not sure...

i would look at uprating your managment - cosworth L6 or L8 or even P8 or full after market system - with a live mapping session to really get the best from it

steel rods and pistons

it all depends whats in the skyrocket, how much are you looking at spending?

make sure your car can handle the power though, good tyres, brakes suspension gearbox and clutch will be needed

if your getting a new gearbox you may as well get a diff too which sadly is more expense

EDIT: i wrote the first reply then the interent died and i didnt think it had posted so i wrote this one out, bloody computers