a fire started

One possible scenario is as follows. I'm not sure if it can apply to the TR, or a fuel injected car, but it does to the older carb V8 engines.

For whatever reason, you lose ignition on one single bank. Power goes down next to nothing. You are dumping unignited fuel from one bank through the exhaust, and importantly, the catalytic converters. The catalytic converters are SO hot that they'll actually ignite the unburned fuel. Your "Slow Down" lights will come on as a result of the cat's temperature exceeding some amount.

The fire starts at and around the cat and goes from there. You're lucky you didn't burn the whole car down!

You need to flatbed to a mechanic and diagnose the ignition system on each bank. Also, a failed alternator or ignition coil or other electrical system component could be a contributing factor.

 

A malfunctioning coil would definitely cause the scenario above - no coil, no spark.

 

I have heard that cat fires are not uncommon on the TR.

 

Check the wires by the distributor cap on both banks and see if any came loose- I had this happen on my TR 3k miles after a shop replaced the wires. I came to find out that 1 of the wires wa snot screwed in properly, worked itself loose and arched causing a small fire and melt down of the distributor cap. Its very rare that cats heat up and cause a fire on the TR.