Main bearing replacement
 

I went to purchase so new replacement big end/conrod bearings and main crankshaft bearings for my 440 yesterday,just wanted to replace while I had it apart,not needed regrind just replace as was,the conrod bearings were standard no probs to get,but the mains there were two types,mine has casting stamp of 1974,the bearings varies,they were different from 74 0nwards, the two different bearing sets are made by Clevite 77, and the difference they are saying is the centre bearing the one with the thrust, the sets say "bearings 440 exept with 3.555"-3.675" main bearing flange OD". Im not sure which bit to measure when they refer to main bearing flange.
Does anyone know which bit they are refering to please,
Many thanks in advance
Grant:)