jonwvara 

I have a nearly new (was NOS when I bought it, but rode it a bit on a trainer this winter) Pro Compe 5-speed freewheel with 14-17-20-24-28 cogs. I'd like to replace the 28 with a 34 to make it into a 5 speed Suntour "megarange." I realize I probably won't be able to find just that one cog--I'm resigned to buying a 14-18-22-28-34 freewheel on ebay and plundering the 34 cog from it. But I'm not clear about compatibility. Will a cog from a New Winner freewheel fit a Pro Compe? If not, what should I look for?
Since I've never switched freewheel cogs before, I'm also wondering how hard that is to do. Do the cogs tend to thread on super tight from pedaling pressure, as the freewheel body tends to do on the hub? I often use a 4-foot length of 1 1/2 inch galvanized pipe as an extender on the handle of my big adjustable wrench when removing freewheels, and it seems to me that something similar might be necessary when using a pair of chain whips to unscrew individual cogs. Or is that not a problem?