What elevation do you live at? Most 302 engines are timed at 6 for sea level and you add 1 degree for every 1000 foot in elevation. I live at 6k and I used to keep mine set at 12 btdc for around town but would turn the timing up (add a couple degrees) when I went to the hills. You said you had it set at 10, do you live around 4k feet in elevation? That will have a pretty good effect on how it drives. But like I said, those Holley carbs are crap on an EB. I know what you have, because I had the same one 2 bbl, 500 cfm. I had mine tuned to the vehicle 2x by a professional engine builder and it NEVER ran right unless I was doing 60 mph down the highway. As a matter of fact, it almost caused me a roll over on a trail. But try timing it. The Holley will run great at high speeds/RPMs but it will leave you wanting something better for anything low RPM or off road.