You really need to decide on a spec asap mate

if we know what were aiming for then it can be built right first time and won't have to come apart in the future!

Do consider your transmission though,400bhp will kill standard 4x4,450bhp will kill even uprated stuff.......for over 450bhp you really need the whole transmission done with thick wall diffs etc.

if i were you i'd try to get a ride in Ad's cossie and see if that feels fast enough for you....if it is then go for the T34.55 from turbotechnics. if it's not then a T38 or a small NMS spec GT30 would be best (Karl has his own spec GT30's now that would be ideal for your car i reckon,but i think they are a little dear)

another thing to add to that price i gave you is the cost of a WRC gasket,Grp A won't be enough for anything bigger than a T34 for a very long time.....

As i say,either a power figure or how you'd like it to drive then we can go from there.....you may need more work done to the head too at this rate including new cams