What Thrust Bearing?

[Bonzo]

Hi James

Sorry to have misslead you a little .... When I say that the gearbox shaft is supported at the flywheel. I in fact mean, supported in the crankshaft.

for some silly reason I thought if I said flywheel it would be easier to understand
Forgive me, I have had a stressfull day

The spiggot bearing fits in the crankshaft ( This will be drilled, ready to accept the new bearing )

It is highly unlikey that you would be able to remove the old one without destroying it.
Probably be wise to use a new one in any event, there could be a fair bit of wear on the old one