Floorboard replacing

[Jimmy_bronze]

Hi everyone. First time on here.

I need to replace a length of floorboard which has split. The floorboard is original 1930's and the width (110mm) is not commercially available from Wickes etc.

I can get 94mm which would leave an 8mm gap each side. Would this be ok to fit as is or should I fill? The concern is overtime a dip would form in carpet that has been layed over the top.

To me the safest thing to do would be to fit pine slivers but am I just overcomplicating?

Obviously an alternative is try and get a reclaimed length with the same width but I'm not sure how reliable or long this would take?

Cheers
James