Glenn,
You are correct about the C205 not ever being called by Cessna a Centurion. And, interestingly, the first Cessna 210 introduced in late 1959 production was NOT called Centurion, but was constantly updated. The C210 initially was powered by a Continental IO-470-S of 260 Hp. The first Centurion was the C210D model that introduced the name Centurion and increased power to the IO-520 with 285 Hp. The C210 had wing struts until the C210G model introduced the cantilever wing. C210 production ceased in 1985.
The first C205 was a fixed landing gear version of the C210B with same Continental engine IO-470-S of 260 Hp and optimized for utility roles. Advantages were lower empty weight, more load capacity with more interior room, fixed gear with less maintenance and insurance costs than the C210 retractables.
The C206 replaced the C205 in 1964 and was called the Super Skywagon initially. The C205 never had a name other than its full model designator, which was a confusing mouthful.