measurement of length for block and tackle replacement

A home owner from New Mexico says:
Your site shows the way to measure length is from 1 metal end to the other.

I have two units in hand, one is stamped 28 1/4" and the other is stamped 28. In both cases the metal "barrel" is 1" longer than the stamped lengths. How should I order the 351 series from you?

Also, I'm unsure how to determine the weight says 28-3 LH5 CMC 24 and the other, which may be original, is marked 28 1/4 3 8K. I'm confused and appreciate you help. Thank you.
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Paul from SWISCO responded:
Yes, the length of the metal channel for this kind of balance is usually 1" longer than what's indicated on the stamp. That's normal. If you measured 29", then that's what length you should go with.

Harder to say about the option. We have a chart of options under the S351-29, along with how much weight each option can hold up. I recommend that you weigh your sash and compare what you get to that chart so that you can be certain which option is best.
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