The bottom end is what my buddy was told it was from the person he bought it from. A built 383. Not to long after purchasing it I got a little sceptical. Measured the stroke at 3.75 and crank is forged. Connecting rods are forged H beam 6.0" SYSC rods. Need to do some research on those. Never heard of SYSC. Pistons are probes. Possibly forged. Thats what my eyeballs and depth gauge gave me. I need to run some #s for exact specs.