Modular blocks are cast in either aluminum or iron at either the Windsor, Ontario, or Romeo, Michigan, plant. There are a few differences between the Windsor and Romeo blocks, but the cylinder heads all interchange. Look for a W cast into the boss near the starter to know if your engine came from Canada or not. Regardless of the material used, any modular block is good to at least 800 hp. That means the block in the taxi rotting in the corner of the junkyard has just as much performance potential as the block in the '03 SVT Cobra, the so-called Terminator engine. The blocks use a deep skirt design with cross-bolted main bearing caps. From the factory, they are a lot stronger than a 5.0L block. They have a reputation for longevity, too. Our sources have seen modular engines with 500,000 miles that still meet the factory specs. All 4.6 blocks can use any 4.6 crankshaft and rod bearings, but the Windsor and Romeo blocks use different main caps and bearings.