For comparison you might consider adding the Blockley 550/15 tyre. It's actually the closest size to the original Dunlop 5.90 x 15 RS5 being only 5mm smaller in diameter.
Another factor is that it is not recommended to vary overall tyre diameter by more than 3% from the original specification which gives a range of 640mm - 680mm as ideal and you need to take into account tyre wear as well so one of the Blockley sizes would be outside that range once worn by more than 1mm.