My f is a couple of years younger than yours & I really can’t remember how many seams it had originally & I’m guessing it now has one, laterally over the (glass) rear window.
The two seamed one had left & right side pieces & a central section which encompassed the zip out window. IIRC.
But
I’ve just lit the fire, which is roaring up the chimney, making my morning very pleasant indeed, so if you think I’m going out into the eye of the storm, down to the garage in order to count soft top seams, I’m afraid the answer is no.
Anyway. I’ve always been an adherent to the the first iteration of a design being optimal for the job & any subsequent changes being governed by cost, however in this case I suspect that it was a better (as opposed to cheaper) way of doing it.
The chances of finding a twin seamed soft top to keep the car period correct would be slim, so I would get yourself, providing you don’t want to buy the cover & a newer frame, to fit at your convenience, a ready done offering from the several suppliers.
I bought mine from MGFnTFBITZ I Glossop for no better reason that I’ve had parts from them for as long as I’ve had the car; they are a professional & personable crew. Five star.
PS I did ultimately go down to the garage, I’ve just had some 20mm threaded rod delivered for another job; it’s not all MG fun you know & as I thought I have just the single lateral seam.
M