...by eliminating some duplicates, and plurals, I've cut it down to 100. It's a transmission service center, so the phrases are things like "auto transmission repair" and "clutch rebuild." I need to add these keywords to their site, but from what I've read 100 is still too many, but I"m not sure how to narrow it down. Does anyone have any suggestions or analysis tools or sites for this kind of situation? Any feedback is appreciated.
Try to make long tail kywords by those keywords you have selected. You can use longtailfinder.com for making long tail keywords.
I don't understand the problem... Make a content to support new keywords... keep density really low (like 1.5% max). Tell your client that you need articles for that kw's, that you don't want to screw up the site just by injecting new keywords in old content