Hi Cathovisor, I regret hard wiring the set for 625 only but that was the norm in those days. When I did the single standard conversion the set was well over ten years old and was considered nothing more than an out dated model, the sort of set that would have been used as a customers loan set.
Now the 2028 is almost fifty years old it's a survivor and as you say it deserves returning to it's dual standard status.
Fortunately, the IF panel is still in it's original state, complete with the standards switch, but it does need realignment.
I was lucky to find the switches, one was removed from a very rusty TMB272 and the other was found in a TV shop in Scotland.