The simplest thing to check would be the universal joints on your drive shaft. See if you have any play in any of those universals. The springs in the center of the clutch disk could also be out and cause a clunking. MGB's also have thrust washers in the differential that wear out and cause a clunk in the differential.
You're a clunk-head...
It could be that the transmission fluid is low, or it could be that mechanical parts have worn down. If so, it may be time for a replacement.
sounds like a motor mount is loose or needs replacing
bad synco rings
Are you sure it is the transmission that is clunking? It could be the u-joints on the drive shaft that are making the noise. When the u-joints on the drive shaft are bad, there is an audble clunk when you accelerate and when slowing down (basically the same motions you go through when shifting gears).
The rubber isolators in the engine mounts have worn out or the CV joints in the drive shafts are worn out.
Loose universal joint(s) in drive train.
If the ticking is in time to wheel speed and most noticeable on turning I would suspect an outer CV joint. An inner axle joint might clunk when shifting into reverse. Maybe they're on the same axle. Other possible causes of clunking are worn-out motor mounts.
how does a coil work in a MGB
Sway bar bushings
Check for Rheumatoid arthritis. Cervical spine X- ray.
MG MGB was created in 1962.