Big small block stroker cranks

So I have seen some threads talking about 4.1" and larger stroke small block cranks.
I am assuming that these are standard 4" stroker cranks with offset grind rod journals and chevy rods. Is that correct?

Anybody know what the reasonable stroke limits are for a factory block? I know depending on rod choice you sometimes need to clearance for the 4" stroke near the oil pan rail. Seems like there would be a limit in this area for addition stroke. Anybody know what those limits are and with what rods? Also are there any other areas that would limit stroke before the pan rail area?