Since we are talking about software written today, not just software available in 1987, X386 (which came out with X11R5 in 1991) was more than capable of running on a 386-class machine from 1987. Granted, a 386 class machine with 1MB of ram and a hard-disk would have been pushing $10k in 1987 (~$27k in 2024 dollars), so it wasn't a cheap machine.
Since we are talking about software written today, not just software available in 1987, X386 (which came out with X11R5 in 1991) was more than capable of running on a 386-class machine from 1987. Granted, a 386 class machine with 1MB of ram and a hard-disk would have been pushing $10k in 1987 (~$27k in 2024 dollars), so it wasn't a cheap machine.