Originally Posted by russxr67
block mods are not needed for clearancing. Unfortunately its not quite as simple as swapping in a crank. Custom rods and pistons are usually part of the equation.
As Russ notes, you likely need custom pistons, however, there are stroker combinations that can use off-the-shelf Chevy rods, which tend to be moderately cheaper than most Cleveland-specific rods. Clearancing may be necessary depending on your exact combination, but generally it is not required. A 4.000" stroke crank with H-beam rods usually needs some block clearancing performed.
Nearly all aluminium rod combinations require clearancing due to the thickness of the big end/caps, though they are not very practical in a street application nor for many strip applications.
There are other details that make it more work to swap in a stroker crank. Most of the crankshaft manufacturers' stroker cranks are really 351W cranks with Cleveland main bearing sizes, which is what I call an "SVO" style crank. That is, they are designed for the Ford Motorsports SVO blocks that are basically a Windsor block with Cleveland main bearing diameters. Nobody, it seems, has anything to do with "real" Clevelands these days. In some ways it is even worse here in the US due to the short production life of the engine.