This post on the IMDB mentions cuts made for an 'R' restored to the unrated DC.It does not mention alterations to the climax but I'm sure Glickenhouse mentions in liner notes the MPAA disapproved of the Exterminator evading justice.
http://www.imdb.com/title/tt0080707/...read/105627954
EDIT -Apparently certain countries disapproved of the "happy" ending on release so the climax may have been altered overseas & not in the US after all.