If I recall correctly for '74-76 cb550 doesn't use a stepped stem, it is a constant taper after the knurled part until it reaches the knurled part at the other end. So, I like the idea of the correct length as I want my signsls to be old school cool not cafemodern. Heck, They may have a Ulra bright low watt LED bulb in them that is brighter than the sstock unit but less current but, they are gonna look period correct.
Also, '77-78 (or whenever the big lights hit the cb550) might have been '76? the fork ears were changed to a gaiter-less fork design (77-78 I believe) and the mondo big indicator/turn lamps become standard. The big indicator lamps didn't have a separate stalk, it was built-into the fork ears on the CB550 and the indicator lamps were mounted lower out of any possible flare from the motorcycle's headlamp by the position moving down the fork ears 4-5 inches. Granted Halogen lights had not gained widespread use yet, so it is interesting to see that change for safety. (It is my supposition that is why they were moved.)
David