I just re gasketed all the windows in my '73. The PO had done a partial job, so I had some windows with D gaskets, and some with the original two-pronged stuff you describe. I tried some off-the-shelf D gaskets from Lowe's, which were self adhesive. Didn't work out too well. Adhesive didn't hold up even after only a couple of months. So I ordered enough of the two-pronged stuff (still for sale at Out-of-Doors Mart
) and a couple of tubes of 3M gasket adhesive and did all the windows. The two-pronged stuff is more expensive than the D gasket--I think I paid around 77 cents per foot. So far, so good. The adhesive is doing a fine job of keeping the gaskets in place (though it was messy as heck to work with), and the gaskets are keeping out the water.