Current Projects chat and miscellany

So I'm considering replacing my 49d's with something with a bigger BCD and also less teeth.
Currently on 52/17 and its a bit tough on the old knees so might scale down to 50/17 and then 48/17 if its still a problem.

Any reccomendations on suitable replacements that would look good on a 1960's Bob Jackson?

Just swapping your cog for a 19t would be easier.