808 Duster....Listen to Rob (crackedback) here. He knows what he's talking about. Every comment he's made is relevant and helpful. Try a diff carb like a 750dp, do a compression check too, and go from there. Report back and let us know what you find. Rob is right with that mph your not making the power your combo looks like it should on paper. Don't go crazy with valve bodies, 4.56 gears, and rear suspension mods and lightening it up for craps sake, gimme a break. Do a comp check, swap a 750 on it. Read your plugs. What are they telling you? Those are 3 quick/easy things to do that will tell you a lot.
Good luck! You'll get there....heck, my junk stock '78 smog 360 with a bazillion miles on it & 3.23's ran 15.0 @ 90mph in my 70 Duster on a 275/50 drag radial and just a 625cfm carb on the stock iron intake and headers with 2 1/2" duals, your leaving a lot on the table. You'll get it, don't worry.
