The 350whp is very achievable, it has been done a countless number of times.
The cheapest was (as lsturbohatch) mentioned it the Vitara/Eagle rod combo for the block. You can use the stock head, but you can also upgrade to the Zex/Comp cam with springs and retainers to get it there a bit easier.
Keep the D series...you'll surprise most people when you murder them at the track w/ a single cam.

As for kits we offer several kits built to the customers specs.