350bhp is achievable from a GTT lump, but not going to do it with K-Tec parts, you need to going down the custom built route to get the power you want.
Seperate oil cooler is handy if your going to use the car for track days etc, as for the copper core rad comment above, I would personally not use one, they are not as strong as the standard item, also not worth going down the route of low temp stats etc, keep all that standard