Holley used to make a TBI system for 6 cylinders that didn't require programming. They still make a 670 CFM Projection System for V8's that uses several turnpots for tuning, no computer required. It costs under $900.
I installed a 2 injector Holley Projection system on a V8 about 15 years ago. It ran great for a 100,000 miles. Just STP Super Concentrated Fuel Injection Cleaner was required in the gas every 3 to 4 months or the injectors would plug. Straight forward installation. Great starting and drivability. The inputs to the controller were engine rpm, throttle position, and coolant temperature. Later a exhaust gas oxygen sensor input loop was offered as optional. The turnpots tuning adjustments were for low rpm, high rpm, acceleration, and cold running. The larger 4 injector units also had a mid rpm adjustment. With the controller in the passenger cabin, you could tune the system while in the driver's seat with a screw driver, or your finger nail.
Holley has a current system for 6 cylinders, but its more expensive and requires programming. I'm not sure why the Projection 502-20s system (for V8's) can't be use directly or mated with the available 400 CFM throttle body for a straight 6. Engine rpm input to the controller or the shape of the fuel calibration curves maybe? I called Holley tech services once on the matter but they weren't very helpful on the subject.
http://www.holley.com/502-20S.asp 8 Cylinder 650 CFM Turn Pot Tuning
http://www.holley.com/950-20S.asp 6 Cylinder 400/650 CFM Programmable
