I had 4 barrels with three different key combinations between them.
One key and one barrel that matched the key.
I stripped down the three barrels that the key wouldn't open and emptied out all the tiny springs and tumbler pins (45 differing pins

Then I carefully removed the first spring and pair of pins from the working barrel, measured them with a vernier caliper and then went through all the spare pins to find a matching pair.
After putting the donor pins and spring into the first hole of one of the spare barrels I tried the key and it worked

I repeated this method one at a time until I had filled each hole in the spare lock barrel, checking the key for each pin as you don't need much of a variation for it not to work. I soon found the "that's close enough" method wasn't going to pay

In all the pins I had, only one needed to be filed down to match what I needed.
Half an hour later and I now had a matching pair of working locks. This was very satisfying and quite therapeutic

I had better get a spare key cut though as I only had the one. The key was the one I found by chance in a rusty old magnetic keybox hidden inside the front bumper of the Demon and it's like brand new. I had been driving around with it under there oblivious for nearly two years

I had a key for the drivers side but it didn't do anything else. The one I found did the passenger side

The newly built ones will now go on the Dart. Not that they offer any real security but it does stop oiks letting themselves in at shows etc, which to my surprise I have had the NSHRA Old Warden in the past.
Anyway, here's a couple of photo's if it's of any interest
