The correct distributor is a Lucas 18D2. As fitted to my 1959 5TA.
Without checking, I think the one you quote is a pre-unit distributor with different fitting and centrifugal advance characteristics. I think that the drive shaft will be too short for a TA bike and also different.
I think a 3TA distributor will fit physically, but that is likely to have the wrong centrifugal advance characteristics too.
Jim.