Yeah these big market drive-ins on opening day would definitely be 35mm http://faqs.starwarsmovieposter.com/images/usesbad.jpg

I would think for the kind of wide, national re-release Empire had in 81/82 they would have had to make some new prints, the ones from May of '80 would be pretty beat up by then, (playing around the clock in some venues that first week or more). And they would have made new 70blowups from the same source as the 35s, an internegative I guess? Which would have been the more standard EMPIRE by then.