Flat sequins should do just fine: https://www.ebay.com/itm/20mm-PVC-Flat-Round-loose-Sequins-Paillettes-sewing-Wedding-Craft-Accessories/224230182521?hash=item3435290e79:g:6S0AAOSwDxdfq18B
Wow, that looks so nice. Man, there must have been a million of these things on the road back then. Dad had a '79 2 door with the "bent glass" rear window.
Love your building style and paintwork. The Mopar is particularly realistic, and the color combo on the Willys is flat out SHARP! I'd like to see that color scheme on the '63 Impala! ( one of my sentimental favorites)