Transformer Rewind?

["Garth van Sittert" <garth-at-mediasupplies.co.za> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi
 
I have recently laid my hands on a resonably large transformer that I
intend to rewind to my coil specs.  It originally weighed in at about 20kg
with the copper windings.  How do I calculate the VA rating from the core
size and ampere turns/windings for the primary.  The core measures as follows:
 
 
       ==========
       ==========
       *==*  *==*           height = 10 inches
       *==*  *==*           width = 7 inches
       *==*  *==*           sectional area = 4  sq inches (2" x 2")
       *==*  *==*           bobbin height = 6 inches
       ==========
       ==========
 
There are two bobbins (*  *)on the square shaped core.  I am hoping to get
at least 3kVA out of this baby.  Is this wishful thiking.   What size/guage
wire do I use for x current.
 
Thank you
Garth (SA Coiler)