Check the listing for details. KING MB557SI Main Bearings Set Kit for SBC Chevy 305 307 350 383. Condition: New. Listed at 25.18 USD. KING ENGINE BEARINGS This listing is for a new set of King main bearings for large journal Chevy 262, 267, 302, 305, 307, 327, and 350s. P/N MB557SI (standard or oversize). The "X" suffix bearings have .0005" thinner bearing wall that provides .001" extra oil clearance; e.g. STANDARD X, +.010" X. Alecular material is used exclusively by King. It is an alloy of aluminum, tin, copper and several other elements. Because it is an alloy, it maintains its properties throughout its entire depth, delivering consistent and reliable performance. These bearings do not have enlarged chamfers required by most aftermarket forged steel crankshafts. We also carry these in the King Race series bearings, if you require a chamfered bearing. See our ebay store for other Chevy Bearings, and more! FREE SHIPPING WITHIN LOWER 48 US-STATES