Thanks guys. I just might try that electronic listening idea, because even if I'm not having a problem, I could play around until I did, and would then know where my limit is.
Sparkplugs look pretty good. When I did have detonation with the engine prior to re-build, I noticed the plug porcelain was sparkling white, although I didn't see any aluminum or other specs on them. I should pull a few again. Due to the engine design and coolant flow, my #1 cylinder gets the hottest and is more prone, so I'll at least check that plug.
I havn't been able to think anything up for exhaust baffles, but I'll keep thinking.
I have to get some more test driving in and pay more attention...maybe get a video so I can post it for all to listen to.
One other interesting note, is that even with my timing set at 20/38, I didn't have that bark/crackle until I re-set my valves. Silly me had them set with too much lash as I went with the Ford spec vs the Crane spec. Memory doesn't always serve me well. With the lash set to Crane specs the cam overlap comes more into play (which could be responsible for the change in sound) and the engine felt a bit more snappy down low as decreasing the lash advances the valve opeing times a bit. The bark/crackle went away again in hot weather when the weak ignition wasn't doing its job, but came back after I made changes to improve the spark quality.