What can I do to change the shift pattern on a 45 flathead 1941 3 speed transmisson so to change it from 1st gear being forward to first gear back. I've heard all I had to do was put a 47 shifter drum and call it good. Is their any timeing marks on the 47 drum and 41 shifter gear to be reconfigured? Is their a specific gear that the trans should be left in when removeing and reinstalling the drums? Im doing this because I have nice origanal 47 tanks which use the 1st gear back shift patern.