Who did you buy from? IMO it's a good idea to check it out before installing. I've bought two crate short blocks in the past and found problems with both. One was bored .040" over and I had instructed that I didn't want any block more than .030" over, plus they sent the wrong year block that didn't have the threaded hole for my clutch linkage. The second place I bought a short block from didn't set the clearance on the main thrust bearing correctly, was way too tight. When I told them I had to set the clearance because they didn't get it right they told me that I just voided the warranty!
