Replacement Channel Balance for Single-hung non-tilt windows

I have an original window that is about 33 years old. I installed new take-out clips that I purchaed from you and have removed the channel balances. I need to find the right replacement. I also need the plastic pieces attached to the top-side of the sash that keep the channel balances in the sash. The channel balance is exactly 31 inches long excluding the plastic ends. The number stamped into the part is 3020 followed by a superscript that is either a D or P. Thanks in advance for any help you can provide.

I believe I found the correct replacement parts after reviewing all the options on your site. But I would like to confirm this before placing my order.

31" SERIES 377 CHANNEL BALANCE
Product Code: S377-31 Option 3020

Also:

TOP SASH GUIDE PAIR, PAN AM
Product Code: 18-042

Could you confirm that whether you agree or disagree with my findings? TIA