I'm running a twEECer but it's mostly because of my cam. What year is your car? The stock computer doesn't really care about displacement, it's usually a bigger cam that throws it off. A tuner will definitely help your tune, obviously, but I don't think it's neccessary.
I assume you're putting in new pistons, but really the alphabet cams are not so great anymore. Try a Comp Cam or get something custom ground. Just get pistons with valve reliefs and check your clearances.
The pistons will take just about any cam, they are reverse dome 14.2cc dish.
What he didn't mention is the car is a blower car, the F-303 although not perfect will work as a good blower cam. The PMS system from Anderson Ford Motorsport works very well and is a piggy back style system, it will allow changed to the tune of the car and is a good investment in having the car tuned to maximum performance of the combo.
Can you run a stock ECU with no additions, yes but with the PMS or other tuner the fuel curves can be tuned for drivability and power, instead of allowing the stock Ford program to make the settings what FORD wanted them to be.
rick the engine man (im buying the motor from him) ya i would of asked you but i didnt wanna bother you to much iwas just currious to get other views on this subject also
F Cams usualy start producing power around 2500 rpm what have you got behind it? An AOD? a C4 a T5? If its an aod or a c4 your gonna need a big stall or when you hit the power band the car is gonna sound like the trany is comming out of it and you'll be sideways, if your at WOT that is