The inner and outer sections were only spot welded at the perimeter, not across the surface. Those "blobs" are an adhesive/sealant that was probably meant to stay pliable for the life expectancy of the car. Unfortunately after 40 years or so its hardened and now come loose.

Since this adhesive/sealant is applied PRIOR to the halves being put together, the tough part is going to be duplicating the original squish pattern.

As far as what to use, I don't know if there is an exact product on the market since technology has changed these materials significantly but if it were me I'd use a paintable body sealer. You'll have to work with clean, bare metal as was originally done or it will just pull off again.