1982 aluminum window balance channels

Thanks for posting. It looks like you have a 28" Channel Balance (not including the nylon fittings on each end) with a 19-002 Top Fitting. For the bottom fitting, I'd like you to measure its depth, or 'heel-to-toe' measurement. The image below depicts what I'm talking about for two types of balances, the Series 380 and Series 385. See if your balance's shoe matches one of these, or is in fact greater than both (I think it might be). Let me know what you find. 

Comparison of the S380 and S385 balance shoes.

So long as the depth is indeed 1", then the S380-28 should work for you. For a stamp option, choose 2730.