Structural body rust damage required 50% new metal. New panels much more resistant to rust though so worth it.
I have blown up 5 triumph engines since I have driven the car! but they are very quick and easy to replace. The engine oil in triumph spitfires overheats especially when in slow moving traffic the result low oil preasure and extreme wear on the big end bearings. Fitting an oil cooler is essential if you want an engine to last for more than 10,000 miles! I wish I had fitted an oil cooler with the first engine for it was the fastest one.
I have replaced the gear box for a better one, but later type gearboxes give little trouble.
I have replaced the entire braking system except the pedal. I used high specification parts. The rear cylinders will always sieze if you leave you car laid up outside over winter. Replacements are inexpensive however.
The electrical system took years to finally fix. Always carry spare reel of wire in the boot.
When replacing the starter motor the altinator and distributor I fitted modern equivslents. This by and large has made the car a reliable runner.
After having the whole right side of my car torn off by an encouter with an out of control combine harvester in a narrow lane my car is a little like robo cop or darth vader. It's made up of mostly replacement parts!
The Spitfire is a fantastic car. It can be used everyday whatever the weather. I was able to drive up a steep snow covered hills last winter where others had failed even including a 4X4. I think this was helped by the fact the Spitfire is rear wheel drive and is light it was able to skirm its way up the hill. I couldn't believe it either, but it's true the Spitfire can be a used as a snowmobile.
Needless to say the handling is dangerous and therefore fun. I have retro fitted standard skinny wheels and tyres for more fun at lower speeds.
I also have a Mk1 1800 Golf GTi (the 109) which totally goes faster than the Spitfire, but you find yourself easily going too fast in it.
So I have had a Mk1 Golf Gti for 7 years and the Spitfire for 12 and I choose to drive the Spitfire 90% of the time.
So there we have it all in all the Spitfire is more fun than the Mk1 even though it's not as reliable!