the good news is, your still working on a Chevy lol GM got smart and only uses Chevy engine these days, no such thing as a buick or pontiac engine, they are all Chevy's now.

check the grounds on the bell housing yet?

if they check out ok, tight, clean, and not broken, it could be an ignition switch gone bad.

the grounds are above the starter on the bell housing bolt. the neg ground cable from the battery bolts there as well with 2 smaller grounds.