I've seen em with most of the fins rusted off but still had 1/2 of em or so. Water quality and time will do the trick.
As a general rule you can start with the middle bolts and from there cris-cros back and forth reaching both ends at the same time... you will need to start at 40 lb and then go up 10 lb each time you do it till you reach the correct torque. I like to go over the bolts about 5 times.
I think it makes the torque more even and as tight as it needs to be all over.
I run a tap in all the holes and a threader over the bolts most times. Just to clean em up. A little dirt in there might screw up the torque. Fooling an 80lb reading with only 60 lbs.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />