The difference on the 250 engnies is with the bearings outside diameters. Up to 1970 or 1971 they had two different OD's. After that they were all the same OD. The 77 engine should have all 4 exactly the same. The camshaft journal diameters are all the same from 1963 to the end of the 250 production and a cam that fits a 63 will also fit right into any other 250 no matter what year.
The OD difference on the bearings is slight and it is possible to jam a bigger one into the smaller block bore. This of course distorts the ID and the cam won't fit. Either they used the earlier bearings in your 77 or there is a bearing that is not installed correctly.
Is SH718 the number of each of the 4 bearings or is it a number for a bearing set that may be for the early engines? As John recommends, you need to talk to the shop who installed them and get it sorted out.
