So, in my attempt to install the waited for all summer and just arrived engine parts to rebuild my motor in time for the NARRC Runoffs, I have discovered my micrometer can't decide on measurements. Take 'em twice, viola! Two different readings. Three tries=three readings. So, I've decided to chill and wave the white flag...and get another micrometer.

Recommendations?
I'd rather not spend hundreds and hundreds on a tool I use rather infrequently, but, I do want something that will be accurate and repeatable.

Also, the good book calls for measuring the side plates with a straight edge. I've used real straightedges before, I I know they aint cheap. Any ideas on a source that won't break the bank? Is buying used a folly in this case?