Rad bike. Not a prototype. 1996.
1996 Giant MCM-2 - BikePedia
What's wrong with cranks? If you wanna replace them but not the bb gotta get cranks that go on a 107mm bb. Or just get cranks and BB in one go - Pretty much any 68mm bb with compatible 42 or 44 t big ring cranks.
I'm not a fan of Shimano chain, just run Sram 830 on that drivetrain but run the shimano til it dies or you have to break it for some reason.