It seems that I don't have the nut installed on the inside either, and the spring on my cable looks like yours does. I don't have any problems with clutch engagement. I'm pretty sure all that spring is there for is to maintain pressure for the cable to stay in the clutch fork, so as long as it's not binding it's probably fine. Will the cable housing move? Maybe a little, but it's probably just fine without both jam nuts - at least that's how I viewed it when I put my car together. Now, if that spring is binding, that could cause problems, so it shouldn't hurt anything to trim it some, at least so it's not as bound up as it is. But I've been able to adjust my clutch with it looking like yours does.
This is just me thinking "outloud" since I really don't know, but is there a difference between clutch pedals? If so, is yours a stock 302 pedal or was it robbed from something other than a V8 car, like a 4 cylinder or something? I mean as I understand, yours is a V8 car, so it's the stock pedal? Anyway, if it's from something else, the pivot points could be a little different to allow for more or less pressure - that might affect clutch engagement....