Triang Spot-On Models restoration replacement rivet heads.
Taper white metal casting of a Spot-On rivet head with a taper pin to fit into a drilled out assembly post. Drill the post out, file or trim the pin of the rivet to suit.
Dry fit to test assembly.
Use a 2-part epoxy glue to adhere the pin to the in the hole of the post to re-attach the chassis base to the body upper.