Great assessment. I don't think I would ever have found GM# 598757. This 5/8" wide x 27" long x ?/4" high is a perfect fit. A little investigation on AI and my part indicates that this is an obsolete part and not replaced or available by itself. The only way to get something close is with its inclusion in a felt kit like the above mentioned "Repop" kit. Their 27" foam part (cross section below) may be the best available. The other aftermarket option available is to use a single piece of flexible channel to replace the original three parts. I'm going to try the "Repop" kit. I would think that the inclusion of 27" of flexible window channel would be a better option, but that does not appear to be an option in any of the kits and I'm too cheap to buy an additional 8ft roll of window channel. I could always do that if I don't like the way the "Repop" weatherstripping works out. Many thanks.
