Hi Tim, and welcome to the HUBB!
The starting point for your search should always be the Shipments page (see menu on your left under Getting There). Although we don't have a shipment report for India to Istanbul, we do have a number of shipments from Delhi to Bangkok via Air India cargo, which will give you contact details in Delhi as well as an idea of costs and the procedure. Click on <A HREF="http://www.horizonsunlimited.com/tripplan/transport/shipping-asia.php#DelhiToBangkok" TARGET=_blank>
An agent which many travellers have used in Delhi, (most recently 2001), is Aqua Travels - Rajeev Bhatia was the manager. They may be able to get you a better rate with another carrier. Their contact details are also on the Shipment page (link above).
Good luck, and please let us know how you go, for the benefit of future travellers.
"It matters not what goal you seek
Its secret here reposes:
You've got to dig from week to week
To get Results or Roses."
'One world, two wheels'