To make it reliable you're going to be spending likely well over $10,000 in parts. I'd recommend rebuilding the entire engine from the bottom. If you search around there's tons of information all over the internet on multiple websites that should give you a basic idea about how much work will be involved. You'll most likely be upgrading the transmission to at least a 6-speed as well.
Stalkergc has it about right. Build the bottom end (which you might as well upgrade to the 2.5), upgraded oil pickup/baffled pan, injectors/fuel pump, an FP blue, and a very careful tune. Expect to spend lots of cash to make it happen. That list doesn't include any supporting mods. Also, pretty sure that around the 300-400hp mark is when the tmics start having issues with heatsoak and such, so expect to go front mount too