(ET) battery terminal question

[tb <tbamc gbta net>]

Not exactly E-T related but does pertain to 12v lead acid batteries:  I've 
been having trouble with the + battery connection at the battery in my 
pick-up.  The battery is old, and the post isn't smooth but is what I'd 
call 'pock-marked'.  Generally it all works fine, but especially if it 
sits unused a while, it will act dead when I try to start it.  Loosening 
and moving the clamp on the post, just slightly, will then allow cranking. 
 Sometimes it takes multiple attempts at moving it slightly.  

I've cleaned (with a battery post, wire, cleaner tool) the clamp and the 
post many times, without solving the problem.  Swapping a different 
battery into the truck completely resolves the problem which makes me 
fairly certain the old battery--and not the cable, is the problem.  I'm 
suspicious, but am far from certain, the weird surface texture of the post 
is contributing to this, but am unsure how to fix it.

Any ideas or suggestions?

Thanks.

Thon