put together a 408 , aftermarket dampener pulled up against the mid 70's timing cover,took out the thrust bearing.
had crank repaired(welded up thrust ,straightened , turned mains .010 under).
crank does not turn freely like before,will check run out at center main with only the 1 & 5 mains in..... what is the maximum allowed?

I would say if it doesn't rotate freely, then however much runout you have with those particular parts is too much.

I'm pretty fussy about main runout...... I really like it less than .001".
I have let it go with a little more than that, but only if the crank rotates really freely.

How straight and parallel the main bores are, along with the alignment between the bores, along with the bearing clearances, will determine how much journal runout any particular build can safely tolerate.

Be sure to check all 3 of the center journals.

i'll check the other mains......at the center less than a 1/2 thousand

When in doubt , fix it Many crankshaft that are welded are not straighten after the welding and grinding Many standard comercial crankshaft repair shops don't check the main bearing run out before handing it back to the shop or customer Put a dial indicator on the crankshaft with it in the block with the main caps off and check every main journal for runout, let us know what you find out
I've had more than one 273 and 318 blocks with stock cranks and standard replacemnt after market main bearings have tight spots in number two main bearings
Good luck.