NEW 4" CRANKS $250.00 any good?

The good thing about those 4" cranks is the engine makes the HP at 5500 to 6000 rpm so you don't have to rev super high. That should help the cast ones live. My 408 made peak HP at 5900 and held almost level to 6100 until it started to slope down. I've got the mopar cast 4" and it looked great. I don't have many miles on it though.