All Tikka T3 and T3X actions are the same size. Same size action for all cartridges. So all stocks fit all. One size fits all.
The only time the stock size is different is if it's a chassis and the only reason major reason that is, is magazine inlet. To fit general purpose AICs magazines etc, which are cartridge/calibre specific in size externally as well as internally.
In regular stocks and original magazines by Tikka, all magazines are the same size (external dimensions) to fit the same magazine inlet. However every magazine has blocks fitted to shorten the internal dimensions to that of the cartridge it's designed for.