Hydroboost off a 2000 f350. I used my 1978 master cylinder. There is a 2" spacer between my firewall and the booster. I wish I had built a 1 1/2" or 1 3/4" spacer. My pedal sits a little low currently. I will fuss with pedal to get the right pedal height when a pull the brake / clutch assembly to get ready for the hydraulic clutch / zf5 combo.