Red - Doing a grille block on the Insight probably won't be a problem unless you're in a very warm climate. I live in Atlanta and I 'grille blocked' my 1.3L engine Aspire without any major increases in operating temperature. Considering that the Insight has a 1.0L, and how small the grille opening is, I think you'll be fine.
Either way, please keep us posted. Your rebuild is very interesting...
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