Was able to get these all done in one sitting today (normal difficulty).
Fisherman's Ranch - Subaru Impreza 22B-STi '98 - I threw some dirt tires on the car and went. It did pretty well without any modifications. I don't drive this track enough to remember all the corners. I had climbed up to P2, with P1 within reach, but I buggered up one of the corners late in the race, giving up a spot for a P3 finish. Oh well, good enough for the first ticket.
High Speed Ring - RUF CTR3 '01 - I left this car entirely stock -- didn't even upgrade the tires. I probably should have, though. With the stock SM tires, the car needs a lot of braking space. I kept forgetting that and went off the track a bunch of times. Still, I easily blasted past the field by the second lap. Easy win. And CRB, too. Second check mark achieved.
Brands Hatch - Alpine A110 '17 - This is a fun race. I had upgraded the tires to SS the last time we had a WC event with this car, so I went with those. No other changes to the car, as far as I could tell. It took a while to work my way through the field, but I finally caught up to the lead car on lap 4 and took the lead, which I held to the end for the win. CRB, too. Second ticket mine.
Blue Moon - Nissan R33 GT-R V-spec '97 - Going in, I wasn't sure how good the car would perform in stock form. It was well below the 700PP limit. I decided to give it a try with only minimal enhancements -- SS tires, and some aero upgrades. It was a challenge working through the field. Going into the final lap I was in P4 and a fair way back from the three lead cars. The rubber-banding kicked in, though, and they let me catch up as we went into the infield. I got by two of them, but couldn't catch the lead car. Still, the P2 finish was good for the fourth check mark.
Autopolis - Honda NSX GT500 '08 - This took a couple tries. I didn't make any modifications to the car except tires. My first attempt was on RM tires. I got into a crash and spun out a couple times, but it didn't matter much because I wasn't making any gains on the leaders anyway. Finished P10, or so. For the second attempt, I switched to RS tires. That made all the difference. I was making gains on the leaders from the start. I pitted on lap 5 for fuel and fresh tires. Going into the final lap, though, I was way back in P7, contemplating what I would have to change in my next attempt to win it. Then, to my surprise, all the cars ahead pulled into the pits, handing me the lead for an easy win. The AI is weird. Good for the final ticket.
The parts ticket gave me weight reduction for the Porsche Taycan. Add that to the pile of other parts that I'll never use.
The car ticket gave me a Super Formula '19 / Honda, which I already own. It is currently sitting at the low end of its valuation range, at ~465,000 credits. I'll hold on to it until it goes over 500,000 again.