[El Dorado Jim]

what year truck do you have? I am guessing 72 or older,like Jim's70gmc said, if your trans was originally bolted to the cast iron bell housing you will need to drill 2 of the holes out,I used an aluminum one in my 72, but also used a trans/tcase from a 74.....the throw out fork is different for an aluminum bell housing,make sure you get one for a 73 or later