Thanks for the reply, I wasn't sure if the cylinder would bolt on properly or not.
Regarding the carb, it's a 250a. There were several different carbs put in that series of Johnny. PM me if you think it's the one you're looking for.
Here's a picture of it, courtesy of my neighbor to the Southwest:
Chainsawr jonsered 670 chainsaw tillotson hs 250a re-circulating carburetor
FYI, I have a ton (well, probably more along the lines of 70 lbs) of Jonsered 670 stuff. Also Husqvarna 141. And I just picked up a Stihl 08 that runs.
I like 70cc McCulloch saws and parts, and I'm considering sitting at the adult's table and getting an 80cc Mac (800, sp81, 850, etc; I'm not looking for any more boat anchors, though I would like a Super 250).