TR4a shift lever

[Jim Wallace <jim.wallace@netscape.ca>]

I'm putting a TR4a gearbox into my TR3a, and want to use the 3a shift lever.
Just noticed, the bottom of the 4a shift lever, where it engages the 
selector rods, is tapered, whereas the bottom of the 3a lever is square. 
Should I grind the bottom of the 3a shift lever so it matches the 4a lever? 
Was this an improvement for smoother shifting or less wear on the selector 
rods perhaps?
Seems like it, but thought I'd check first.
Thanks,
Jim