All 1932-48 passenger cars and commercial 3-sp trans had syncro 2nd and 3rd gears. They changed and improved the syncro design during 1939. The 1939-48 3-sp transmission innards can be installed in your 35 case but is best to use all the same component unless you are very familiar with the transmissions. Using the 39 and later innards requires the use of a 1936 and later top cover with a 91A 2/3 shifter fork and with corresponding shift lever. An enlargement of the hole in your 35 floor boards is also necessary. The same type 1935-36 rubber rear trans mount and clutch cross-shaft activating arm should be used.
That being said, your 35 trans if in good shape or rebuilt properly will perform very nicely. You could buy a used 39 type trans and have problems with it also, as there is a lot of junk out there so it is hard to know the best solution.
If you were closer, I'd help you sort it out. Maybe someone down your way with some knowledge could help you out.