As far as I know they all did. The several I've seen from the 80's definitely had an aluminum frame, including mine. I'm pretty sure an 84' will be aluminum too.
Could probably bet the farm that the 84 has an aluminum frame (maybe not the same pattern though).
That said, what's the intent? What I noticed on mine is that while they do not rot, you may pick up a crack here or there. And if it matters, perhaps there are common weak spots (i.e. at some point - my 83 broke loose above the back entry door and at the foot of the front end - Both easy fixes if you have it naked).
This confirms, thank you, I'm contemplating selling my 05' eagle to buy a 84 fleet, looking for a little more room.
It does need a "bunch" of TLC, not sure if it's worth the extra length, albeit, the price is tempting.