I ended up using stock Chevy inserts because the 152M's gave ~3/4 thou greater clearance than Std Chevy bearings.
Originally Posted by Nick@AP-Engineering
152M is the STD size Federal Mogul Main Bearing
152M1 is the -.001 Federal Mogul Main Bearing
As I understood the above post he needed STD Mian Bearings so the 152M would be his part number in Federal Mogul.