Today I started the car, after having driven earlier in the day, and the engine sounded strange. Temperature was fine. When the car is actually moving the engine sounds bumpy. It only seems to happen under acceleration, but if I ease off the throttle it smooths back to normal. I haven't driven it hard. Is it the fuel/air mixture, or could my driveshaft have knocked crooked somehow? Or is it something else?

'67 Chevelle post-car
350 sb, '78 truck block w/ unknown heads, voodoo cam and lifter set, doug thorley headers-2.5" exhaust w/ flowmaster super 40 mufflers. That's about all I know, I didn't get much of a chance to ask the previous owner about it...