If your planning on driving the car at all don't put the insulation in, it won't stay in. The Bel Air and Biscayne's never came with the insulation either.
Phil,Checked Assembly Manual 1961 and 1963..........page on installation of hood insulation shows all 1700 and 1800 series only got the insulation. That's Impala 6 banger and V8's. So Belair and Biscaynes are left out by default!! I thought 6 cylinder's didn't get it but they do in the Impala series. I scanned the page but can't post it.