I would think going to www.simplicitymfg.com/manuals/index.cfm?rd=1 and plug in your mfg#'s less the serial numbers would give yu the best idea about usages. 1690547 fits a variety of vertical engiine L&G tractors while the 1690033 fits the 700 AC or 7000 series Simplicity.
Both numbers are listed on the "what fits" on the Simpletractors.com table. Both fit a quite of range of tractors. The 169033 is mainly in the 7000 series and the 1690547 is for smaller units. Go check it out and see if your tractor is listed. You can also get manuals.