I have a 73 Challenger, but when I restored the car, I installed the 70-71 bumper brackets so that I could suck the bumpers in, and I got the correct bumper for the brackets. I just measured mine, and the distance between bolt hole centers is 23 1/4". Are you sure you have the correct brackets? Yours being 19 5/8", that would roughly account for your difference of 2" per side. Could yours be 73-74 brackets?