Is the 5.3 Shortblock the same as 5.7 Shortblock? And if so what are the differences?

I thought the blocks and internals are the same and it is just the heads that are different, not the blocks.

 

I'm pretty sure it's the same design but the block is iron and there are no cylinder liners. The bore is also smaller but the stroke is the same. The cranks also have a different rear seal surface width. The truck pistons are also different i think they are heavier. Also the heads are the same they just have different combustion chamber sizes.

 

Thanks.

 

One guy here on the boards has claimed to have bored a 5.3 to 5.7 specs. His name is romulusmotor or something like that