Yeah, I must say it was a little disheartening to not get the exact figures I was hoping for. While I didn't include it in my original post, I went back and tested the intake at .010 lash. Ended up getting a duration of around 270. Exhaust at .020 lash was about 260. I suppose, looking back on it, I might have set the lashes a tad loose. Tightened the rockers until there was a good drag with the feelers, but wasn't necessarily meticulous about it. Overall though, I was very careful about "quality control" during all stages of my testing.
After all this work on the car, I'm feeling pretty lazy. BUT, I do still have my car's original Slant sitting in the garage. It would be interesting to see what I'd get for results doing the same test. I just have to gather the motivation. I'm really sick of the garage right now!
Either way, I feel comfortable setting this cam at stock lash. There's clearly a .010" difference in the height of the intake and exhaust lobes, and they seem (from what I'm gathering) to be about the height of a stock cam. So at least my testing gives me confidence in that (unless anyone says otherwise).
If anyone has any non-stock theories, I'd love to hear 'em. Otherwise I will keep repeating to myself: "It's a stock cam... it's a stock cam.... it's a stock cam..."
-Matt