Made a dumb mistake today

[blfuller123]

I had been looking for another rear end for my truck to convert it from 6 to 5 lug. I already have some rims that I want to use so I started measuring how I wanted the wheels and tires to sit in the fenderwells. I found a guy selling a late model z28 rear end with posi and disc brakes that just happened to be the width I was looking for. I got the rear end home and started to stick my rims on it and they dont fit. I didnt think to check the bolt pattern. I just assumed that chevy 5 lug were all the same. My rims are 5x4.75 and these are 5x4.5. UGH!!!