Need help with vibration in 67 mustang

[67GTSCode]

Well first off i just wanted to congrats you on ur choice of big block stang. NEWAY

When does the rattleing occur. Mine did this awhile back when i was going 50 or faster. WHen i put it in neutral or turned it off it just started to viberate. It was the driveshaft. Check both U joints if you think that it could be comming from the tranny.. But if it is the engine i can't help you there. But try to see what your doing when it happens. And go from there.

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1967 mustang gt, coupe, dark moss green, black interior, s-code, 4 speed toploader ( only 1546 mustang gt,s-code,coupes with 4 speed toloader ever made in 67) ... Now it currently has a 302 (for daily driving, i am only 16) an edlebrock 600 cfm 4v carb - wanting dual quads - with a comp cam, pop up dome pistons, headers, msd electronic ignition. 3.00 with a ford 9" gears - wanting 3.50 posi gears. Recently accuaired a 390 from a 69/70 ford truck which is being moddified for some seriouse power