will 300x52.5x82 fit on machine that has 300x52,5x80?
Sorry but nope. 300mm is the width of the track. 52.5 and 52 respectively is the mm distance between the bars in the track. That's not much difference, but the sprockets wouldn't like it even if it would fit. The big problem is the 82 vs 80, that's the number of bars. That would make the 80 (bars) track shorter than the 82 (bar) track. I don't know that the track adjuster would allow the difference. Unless you're getting them for free, don't know that I'd try it.
so the extra 2 links would require the idler to extend out further to accommodate the extra length?
That, and that 52 vs 52.5 might not be happy on the sprockets. I don't know the details of this deal, and don't know the machine we're working on, but call Multi Machine and get a price on a set of tracks from them. I've purchased from them many times and their price is usually better than others I get a quote from. Plus, they're in NJ, not all that far from you. > http://www.mmmachine.com/default.htm
Yup, about two inches further. They're both 52.5 pitch?