Here is a nice rarity, a "movie" poster for Future Boy Conan. It's a bit misleading because there was not movie version of Conan. This theatrical release is, in fact, a collection of highlights from the 1978 television series. In other words, it's a cynical cash grab.
There's no doubt Hayao Miyazaki had nothing to do with this, just as Isao Takahata had no part (and fiercely opposed) in similar "movie" versions of Heidi and Marco. These were tv series, and they were structured and paced for that format. There's simply no way you can cram these lengthy stories down into a two-hour highlight reel.
This is just something movie studios did to sucker the public in the days before VHS and DVD. Today, of course, you can just repackage a DVD once every year and charge a premium for it. At least we got this cool Future Boy Conan poster out of the deal. Okay, it's really not so cool. But it's a rare collector's item, and it would look pretty good hanging from my wall. So there.