Catalytic convertor placement

Does anyone know where I can find information for the correct placement of a catalytic convertor in the exhaust system? I am looking to replace the stock catalytic convertor on a 1979 Jaguar XJ6, with a dual exhaust and high flow cats. The older cats had to be closer to the engine to get them to "light off", but todays convertors are placed farther downstream in the system because they "light off" at a lower exhaust temperature, at least this is my understanding from what I have read so far. I however have not found a set length or required exhaust temperature required to the cat to start working. I was thinking of using after market performance catalytic convertor(s) but still looking for info. on their placement.

Thanks for any help,
Ron

If your car has true dual exhaust with dual cats, theoretically, place them as close to the manifold as possible, since there really is not much flow to heat up a dual cat system
Alternatively, try using a single high flow cat. It will make better use of the available heat and flow.
As far as I know, so long as your engine is not malfunctioning, the cat will not get too hot to function, but as you say it can be too cold to work.
I would suggest place it in the original location, since the cars heat shielding etc was designed for that spot. Changing the location may have unforseen consequences, such as being located in an area of low airflow and subsequent possible overheating and fire.

Catalysts still need their temperature to work, and today they are placed much closer to the engine. This especially since we want the cat to work as fast as possible after a cold start, and we also want it to work when the flow is low. The cat is usually placed directly after the exhaust manifold or turbocharger, sometimes two cats are placed in a serie.

If the temperature gets too low it won't work and if it gets too high (usually caused by misfires) the cat will be damaged (the catalyst can be burned away).