lads defender

my cousins lad has just bought his first on the road 90 with a 200 tdi. On his first trip to work the oil pressure light came on followed by plenty banging. After the tow home and strip down we discovered two faults, the bore oiler jet had fallen out and destroyed its self problem solved? No, on closer inspection the camshaft pulley bolt had come loose and a cam roller had fallen off but the cam bearings are damaged. We have found a used block but it needs new shells. How do we tell weather the shells are standard or over sized with the part numbers on the shells, and also the best way to put new cam bearings in the other block to rebuild it.