I'm pretty sure the Taylor Report only applied to the English clubs. Pittodrie and Kilbowie were already all-seated (albeit using bench seats/bleachers) and Ibrox was getting modernised by Murray with his Steel company using it as a prestige project and to generate more income but there was no need to go all-seated until the SPL brought in their own 10,000 seat rule. Celtic and Rangers in particular would have needed to have made changes for European games but not til by the turn of the century or thereabouts. St Johnstone built the first new ground of the post Hillsborough era but they could have had terracing had they wanted to until the advent of the SPL.
The Taylor Report applied to top division Scottish clubs as well. They had to be all-seated by 1994/95 with their standing capacity reduced by 20% per season from 1989/90 to enforce this. Clubs who were promoted to the top division in this time got an extended period to comply, although I can't remember the exact details of this.