From the above post -

"Yep... I had a well known company make a shaft
for me and it turned out to be junk.. was .040
out of true and the balance was way off.. cost
me another $350 to get another from another
company.. now all I use is Dynotech.. they are
local so I can pick it up the next day.. you
wouldnt think .040 is much but it is"


Check a late model Dodge service manual - for a truck prop shaft - .010" is max at the weld ends and .015" in the center. That's for a truck running down the road - 2000 - 3000 rpm.

Now spin that prop shaft at engine speed down the track - 6500 and above.