The block (1.25" x 2.5" x 4.75" in dimensions) has two holes for bolt attachment to the steel track shoe.

The block has a requirement for flatness and surface finish (63 microinch RMS) on the contact base for effective heat transfer into the steel track shoe.

The heat sink block is not a primary structural part and has a minimum mechanical requirement.

The track shoe is a forged steel body.  On first thought, steel might be the metal of choice for the heat sink block. (But steel would add excessive weight to the track, reducing speed and fuel efficiency. And steel has relatively low thermal conductivity.

An alternate approach is to use a low density, high thermal conductivity metal for the heat sink block. That metal would more effectively pull the heat out of the rubber and back into the steel base.