The C64 was released in 1982 and retired in 1994, making any origin electrolytic capacitors in those units currently between 27 and 38 years old. Their insides would be drying out, and are becoming a regular cause of faults or performance issues.
The good news is, these old beasts are also one of the easier recaps of the era, often sporting only a handful of fairly large capacitors that typically don’t put up a fight to replace.
Simply pick your board ASSY number from the list to find the kit you need. All kits additionally include a 4.7nF ceramic cap to optionally replace the 51pF one at C38, to give you a nicer RESTORE key feel!