First, thanks for asking. Here is the fine print on my drivetrain. My springs and hangers are stock 67, rebuilt and rebushed. The 73 A-Body rear axle is about 1/2" wider axle face to axle face than the 7 1/4 or the 8 3/4 that are common rear axles for the 67 A-Body but the spring perches are the same. That makes it a bolt-in for a 67 Barracuda while moving the inside of any given wheel 1/4" away from the stock springs. Further, I had my rear axle rebuild to a 3:73.1 SG. Wanting to road trip the car my calculations required a 28" tall tire with the GV unit giving me a 70 MPH RPM of 2300 with a lockup converter. To fit the 28" tall tires, (275-60-15) on my car required an 8" wide wheel with a custom backspace of 4.125" to get 1/4" sidewall clearance to the springs at the front of the car with no wheel spacers. I had the wheels custom built with that backspace and had them powdercoated to match my 6" wide wheels going in the front of the car. My last road trip after tuning my engine with a A/F wideband was 16.5 MPG at an average speed of 65-70 MPH. RE the GV unit, I am really glad I installed it. I installed the controls in the console of my car and it worked perfectly out of the box with no tweaking at all. I had the driveline custom made at a specialty shop and dynamically balanced. I checked the output/input delta and added a 1.5 degree shim in the axle perches. If I leave the car in autodrive the GV unit wants to engage at the factory default of 45 MPH which is a little too soon for my build combo. I called GV and asked if we could change the shift point up and they offered to send me a chip to change in the controller for $55.00 to change the engage to 55 mph. I declined for now, I will just engage it manually for the time being as I am still breaking in the engine. Hope this made sense and is useful to your needs----------Best regards------------DR----------:)