that is a crucial part im pretty sure. since it holds the crank in place. those cases are all line bored, so you cant even mix and match case parts. that bearing cap is probably machined to match the cases, and the crank journal. i could be wrong about that, and i wouldnt use something from another motor there without double checking if youre not sure. branson might have a good opinion on this.
just dont want to see you do a motor to have the crank thrashing around inside there.
jc