[tooski]

Perhaps my experience will be discounted.
The oem driveshaft in my 68 was dinged enough to cause vibration. I had a 3" ds made with 1310 solid joints to retain the yokes I had.
I have street tires that go up in smoke from a standing start. I reverted to punching it from a 20 mph rolling start. No spin as far as I can tell, I believe I am stressing the driveline fairly well.
Slight wag on the 1-2 shift. I'd like to think that my car would be into the 12's, but I have no dragstrips near me. The 3.07 gear would be a limiting factor.
Did this a couple of times or more a month this past summer.