G'day Frog,
and welcome to the ODK forums.
The correct blades for the 1968-69 Model 550 New Utility [assuming it still has its original blade carrier disc] are Victa P/No CA09262S;
THESE - these blades fit on top of the carrier, which looks like
THIS.
With bolt set CA09305S;
THISAs you say, the New Ute in that pic has a non-original air filter; this model used a 'short' type.
NormK's second pic shows the Type 9C blade carrier used on earlier model Utes, where the cutter blades were flat, and mounted below the carrier. This carrier could be fitted with a second set of 'thrower' blades, which were mounted on top, but the Utes didn't have these.
It might be worth grabbing a few spare sets of blades, as it looks like this particular type is no longer supplied by GA Spares, who are one of the two major aftermarket parts wholesalers.
