The difference in the P&C was with the 026 and early 260 44mm piston saws vs the later 44.7mm 260 saws. The early 260 saws had the ~slightly~ better 026 P&C on them. That is the difference in cylinder 'porting'. The real difference in the early to later 026 and 260 saws is the mufflers. The mufflers got more choked up as the years went by. They also put non-tunable carbs in later model 260 saws to meet EPA standards. I have had a lot of these saws over the years in several configurations. The later 260 saws also had slightly larger air filter. They are mix and match over the years. One thing to note is that a 260 P&C will fit any 026 saw, and a 260 P&C will fit any 260 saw with zero modification required. But they have to be replaced as pairs along with the rings. I have a later model 026 with a 260 P&C that I got from Lakeside Andy here. No issues installing it on a blown 026 engine that was straight gassed.
There are a lot of variables in the 026/260 saw line. Most of these parts are mix and match, but not all. The only difference between PRO and non-PRO saws in this line is the oil pump and decomp. Some of both types had clear gas tanks, most were solid. Some non-PRO saw bodies had a hole in the bottom for the adjustable oil pump, but no adjustable oil pump on them. The earliest 026 saws had a red action lever, a metal recoil cover, an aluminum top handle, a taller tower gas tank vent, and a smaller air filter. The later models had a plastic recoil cover, a composite top handle, 2 different short gas tank vents, a black action lever, and the latest models had a larger air filter. The early ones were made in West Germany. Later they were also made in Virginia. In the next posts are 3 of the muffler models on the 026 and 260 saws. I pulled and compared them at one time and drilled out/cut up the choked up mufflers to flow like the early model ones. That was/is the biggest difference in performance in the line. The mufflers.