Jake, Do we know anything about the starter itself? Has it been rebuilt, swapped out for a rebuilt starter?
I recommend you take the starter to your local "Auto Electric service company". Have him check it out and get and estimate for rebuilding it if it's necessary. Stock alternators, starters are made in bulk overseas for cheap. The parts in them are "not worth the powder to blow em to hell"!
The serviceman can boost the performance and eliminate some of issues you have.
Make sure the starter does not make contact with any hot metal parts. I doubt wrap will do anything.
I bought a AGM Battery from Costco. That sucker packs a punch!
The starter kit looks like the one used in the 65 Mustang. The electric design is a little old. This would make your electric system better but II doubt it will fix the over heating.
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88 restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD AWS LX Lawn tractor 17hp (my daily driver) 2006 Sequoia 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine 2007 Bayliner 175 runabout /w 3.0L Mercuiser__________________________________________________________