[Healeys] Side Change Gearbox, which Laygear ?

[Jerry Costanzo]

I am finally getting around to ordering parts to rebuild my side change
gearbox.  While it was rebuilt during my rebuild, the first gear and laygear
tried to eat each other.  I cannot see an alignment issue with these two gears
but I did note that during the rebuild, the guy working on the transmission
told me the replacement laygear had the wrong number of teeth and I needed a
different one.

The stamp on the top of the gear box says BN4 but the 4 is over stamped with a
7.
The laygear in the transmission right now is AEC 3359 which is a later BN7
laygear.
I see the first gear is the same for all BN2-BJ8 gear boxes, so that would
appear to be correct

Questions:
1.  How do I decide which laygear to order?
2.  I taught my daughters how to stick shift in this car and it looks like
they are someone else forgot that there is no syncro in first gear.  Is there
anything else I should look for that would cause the damage?
3.  All the bearings, syncros, and reverse gear were replace when the box was
rebuilt.  What parts should still be replaced again?

Thanks for your help

Jerry
BN4