I'm not sure what bolt size it would be but I think it's a pretty good size bolt I think there's one bolt on the bottom of it one on top of it and both of them are pretty good size what you could do is do a Google search on your make and model put in alternator and say mounting hardware in the search too and then a schematic a GM schematic should come up and it might give you actually the identification of the bolt I'm not sure if it'll give you the size but you could also call a dealership and they might be able to help you a Chevy dealership good luck.
Search Saturn S-Series Questions
Saturn S-Series Experts
Related Models For Sale
Used Cars For Sale