Throw in your.02 on Torque Converter Suggestion

What does the higher stall converter get me in street performance anyway?

A higher stall converter will let the engine rev into it's power band quicker and easier giving the car a much faster launch.

So let's assume it approaches 300 HP and the 904 and the rear are stock, what do I do for the torque converter?

I agree with Crackedback in that you should look at something in the 3000 stall range. 318's aren't high torque engines so you need to get the RPM's up for it to really jump out of the hole good. Someone else suggested a Hughes converter and I have used them and they work real good for a lower dollar converter. If it were my car and didn't want to spend a bunch I'd look into their 3000 stall unit. With your teen it probably won't quite stall 3000 but it'll be close enough to make it launch good. If you have a couple hundred more bucks to spend a custom converter can't be beat. I run a PTC in my Cuda and it works real good. Nice thing about today's converters compared to converters of yrs. back is they don't slip much at all when you drive it easy. Nothing like the old days when they acted like you were driving a stick car and riding the clutch. Now they drive great and when you nail it they flash up to their stall speed and the car rockets off.

BTW: do you know what gears are in the rearend?