I'd recommend Steele Rubber Products, the size and profile will be correct/exact - everything I've seen from SoffSeal is oversize and incorrect shape - talkin 55-59, but I'd expect all years to be the same quality from both makers
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics