Page 137 of GM Performance Parts 2006 Catalog by GM Parts Direct

Four-Bolt Splayed Main Caps One-Piece Rear Main Seal Sportsman Block (rear). No rear seal adapter. Sportsman Block (front) 135 Four-Bolt 350 Main Blocks B. 10185047 350 Bowtie Sportsman Block Cast iron maximum effort block 4-bolt straight nodular mains 3.980" rough bore 4.090" max bore (siamese cylinder bores) Replaces older 4-bolt, 2-pc rear main seal block P/N 366287 Rear main seal adapter required! 12480174 350 Bowtie Sportsman Block, 1-piece rear main seal CNC-machined cast iron competition block +/-0.001" machining tolerances 4-bolt nodular mains, splayed caps on center 3 mains 3.980" finished bore 4.155" max bore Extra smooth gasket surfaces for better seal Tall lifter bores Comes with rear seal adapter 12480047 350 Bowtie Sportsman Block, 2-piece rear main seal CNC-machined cast iron competition block +/-0.001" machining tolerances 4-bolt nodular mains, splayed caps on center 3 mains 3.980" finished bore 4.155" max bore Extra smooth gasket surfaces for better seal Tall lifter bores 12480175 350 Main, 400 Bore size Bowtie Sportsman Block, 1-piece rear main seal CNC-machined cast iron competition block +/-0.001" machining tolerances 4-bolt nodular mains, splayed caps on center 3 mains 4.117" finished bore 4.155" max bore Extra smooth gasket surfaces for better seal Tall lifter bores Comes with rear seal adapter 12480157 350 Main, 400 Bore size Bowtie Sportsman Block, 2-piece rear main seal CNC-machined cast iron competition block +/-0.001" machining tolerances 4-bolt nodular mains, splayed caps on center 3 mains 4.117" finished bore 4.155" max bore Extra smooth gasket surfaces for better seal Tall lifter bores Four-Bolt 400 Main Blocks 12480049 400 Main, 350 Bore size Bowtie Sportsman Block, 2-piece rear main seal CNC-machined cast iron competition block +/-0.001" machining tolerances 4-bolt nodular mains, splayed caps on center 3 mains 3.980" finished bore 4.155" max bore Extra smooth gasket surfaces for better seal Tall lifter bores 12480159 400 Bowtie Sportsman Block, 2-piece rear main seal CNC-machined cast iron competition block +/-0.001" machining tolerances 4-bolt nodular mains, splayed caps on center 3 mains 4.117" finished bore 4.155" max bore Extra smooth gasket surfaces for better seal Tall lifter bores B B B B

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