[TR] TR3A replacement "laygear" (Countershaft)

[amcewen2 at cogeco.ca]

Last fall I carelessly put the gearbox in reverse while the car was still ever so slowly rolling forward and was greeted
with a bang.  From then on until I put it away the gearbox made a loud ticking noise in reverse and a lessor one in 1st.

I took the GB out over the winter and my mechanic says it's thrown a tooth on the Laygear (Countershaft?).   Moss & TRF
don't seem to stock them for the 2-3A but have an "improved" one for the 3B which I assume won't fit?

Any other source?

Plus I'm told the gearbox will always be noisy from then on.. new or used.

Or I could buy a used GB (without knowing its condition) and lose my overdrive (or xfer the o/d guts to the "new" one).

Options/advise/opinions?

Thanks,

Art