According to my Federal-Mogul specification book, the 248, 270, and 302 engines all share the same connecting rod and main bearing sizes.

Rod bearings: Federal-Mogul part number 1905 CP Standard shaft diameter is 2.3110" - 2.3120"


Main bearings 1954-55: 697 M 1956-63 engines: 4030 M

Main bearings have four different diameters, like 216 and 235 Chevy engines.
#1: 2.6835 - 2.6845
#2: 2.7145 - 2.7155
#3: 2.7455 - 2.7465
#4: 2.7765 - 2.7775

Earlier manufacture date 228, 248. 256, and 270 engines have the same shaft sizes, but they use different part number bearings for some reason.
Jerry


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