I have an old Super 8MM movie projector and a screen. I could sort of have my own outdoor theater in my side yard but each full movie would require like 5 reels. I've seen full movies on ebay like Jaws, and some cartoon shorts that would go well with the drive-in type atmosphere, but 5 reels for a full movie kind of sucks. That's a lot of intermissions while I change reels!
The thing to do is use the condensed films on the 800' reels. Ends up being a reel change every 25 minutes, and usually it's a whole "movie" in that time. If you don't mind spending more money, you can also get one of the ones that takes a larger reel. There's a very expensive Super 8 projector out there that takes a 2000' reel if memory serves.
I've done this with my Super 8 stuff a couple times. Mine has an 800' reel. Last time I showed a Looney Tunes short, the trailer for Sword and the Sorcerer, and the 40 minute version of The Sting (which is very smartly edited down - it contains just the main con of the title).
I got a Super 8 sound camera and projector for my birthday when I was a kid. I had a collection of mostly 200', 400', and 800' condensed movies. Some of my favorites were:
* CREATURE FROM THE BLACK LAGOON (400' and 3-D!)
* IT CAME FROM OUTER SPACE (400' and 3-D!)
* ANIMAL HOUSE (800', mounted on two 400' reels)
* SLAPSHOT (400')
* BRIDE OF FRANKENSTEIN (200')
* SON OF FRANKENSTEIN (200')
* FRANKENSTEIN'S NEW BRAIN (which was a condensed version of GHOST OF FRANKENSTEIN on a 200' reel)
I remember getting a catalog in the mail for FULL LENGTH Super 8mm sound movies mounted on a series of 400' reels. They were really expensive, but I very much wanted to get THE GODFATHER. I think it was about $350 and this was in the late 1970s. A small fortune at that time.
Dunno if you're aware, but there's actually been some fairly recent Super 8 releases. There's a condensed version of Captain America (the Chris Evans version), for example, and a number of trailers. Partly Cloudy (the Pixar short) is on Super 8. There's small print runs still being made by small companies, I guess. They're quite expensive still. If you want to buy a feature, sometimes older films (like Laurel & Hardy) features can be had for $30-$100. Anything in color will likely be $150+. I moved into a smaller place and had to leave my film equipment in storage, otherwise I'd still have em. Greatly enjoyed projecting stuff on film, a lot of fun.