Complex sentence: The Gladiator name was dropped after 1971, after which the line was known simply as the Jeep pickup with J2000 and J4000 models until 1973 then J10 and J20 from 1974 to 1988.
Split into simpler sentences: The Gladiator name was dropped after 1971, after which the line was known simply as the Jeep pickup. This was true of J2000 and J4000 models until 1973, then known as J10 and J20 from 1974 to 1988.