Trying to merge a movie with different release dates and running time.

There are two movies listed in the IMDB that are the same film, but with different titles and one was re-released five years later with a different running time. The Mercenary (1983) at https://www.imdb.com/title/tt0122013 and The Jaguar Project (1988) at https://www.imdb.com/title/tt5791558 . When I try to merge it, the IMDB says I need to have the same date of release. It's probably a simple fix and I'm likely missing the obvious, but I've been trying to make this work for over an hour and I can't get it to work.