Help me stop!

I put the Scarebird setup on a freinds early Barracuda and it would lock up wheels easily and about squeeze your guts out against the seatbelt. You've got something amiss because I would definitely do the Scarebird on my cars if I hadn't already done the 73 & up on one and the K/H on the other before I had any experience with the Scarebird. We did go with the smaller master cylinder diameter on his to make the pedal feel easier but the larger one we used first would lock wheels easily, it just took more leg effort. His pads came from Rock Auto.