We worked on his saw a little, yesterday, we still had to rebuild the carb (after about an hour in the ultrasonic) and clean up his cylinder a bit more, so we didn't finish yet. The case with the broken hole will go in the spare parts stash for now, although trying to fix it still seems interesting... We'll see.
Not sure if everything will fit, we still have to see what to mix and match. Case is from an old 026, cylinder and piston from the ms260 with the broken case. I guess the small difference in bore (0.7mm if i'm not mistaken) shouldn't be an issue.
The old 026 had the smaller air filter and non-compensating carb, I wonder if the bigger, more modern one + compensating carb will fit under the old style air filter cover... We might have to grind some plastic away? Dunno, and I guess the newer style filter cover should fit too.
(He'd like it not to look like a 'thrown together' saw though - something I care less about, e.g. my 1991 044 has non-matching colors, an aftermarket HD2 air filter cover, etc... As long a it runs well, I'm already quite pleased, and esthetics can be taken care of later, if at all).