This page details the pinouts of the connector:
Pin 2 - J1850 Bus+
Pin 4 - Chassis Ground
Pin 5 - Signal Ground
Pin 6 - CAN High (J-2284)
Pin 7 - ISO 9141-2 K Line
Pin 10 - J1850 Bus
Pin 14 - CAN Low (J-2284)
Pin 15 - ISO 9141-2 L Line
Pin 16 - Battery Power
Interestingly it details:
ISO 9141-2--The connector should have metallic contacts in pins 4, 5, 7, 15, and 16.
I have had problems getting just the connectors from the UK. The best place (about 6 months ago) was to get them in from the states - minimum order of 5, the connector & 5 pins (+12v, -12v, sig ground, K line, L line) after import tax, etc cost ~£15 each. Steep... for a 5 pin connector!
Or if you're impatient you can make your own pins and solder wires to them and poke them into the car connector
For those cars who don't have the 16 pin connector and have loads of the 3 pin AMP connectors scattered about the car (145/6, early GTV & Spider for sure... ) these cost about a quid with pins!