So, do you mean guide/ seal diameter against the coil?
Install height on spring interference would require retainer or spring seat work.
The coils are round w/flat damper inner that is short, so the damper isn't near the retainer or floor. They clear stock seals.
I agree with the Hughes specs, too. They definitely tend to their own gear and I can see why.
I'm beginning to think that from what fishy68 said about the '73 587's and what I've read on their site, they are probably aware of that issue, which may not be isolated to that casting and they're just giving a careful number and warning everyone to check for themselves.
