A Roush block (at least my SBF) is stamped "427SR739" for a 351W bored / stroked to 427 & serial # 739 in 2008 at the top rear of the block between the intake manifold and the bell housing. Polished valve covers are "Roush 427R 739" to allow the owner to brag it's a "R" vs. a "SR" if they are so inclined (or haven't contacted Roush for the dyno sheet/ read the block stamping
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