Front Drum brake troubles on a 1964 Dart

A mechanic has it now and is at his wits end on how to fix the front brakes from shaking after freeway driving for around 10 minutes. It seems to get worse the longer it's driven. My mechanical skills are pretty basic. This is the 3rd Dart I've owned, and I had disc brakes installed on my 63 wagon. That fixed the right pulling brakes. On My 66 I had the drum brakes completely redone, and they worked amazingly! So I figured maybe drums aren't so bad let's try drums again but now I'm thinking maybe time to buy another one of those disc kits.