Alright, so I just spent about an hour or so trading wins on the "Criminal Record" race (totalled about 40? 45?) with some patient soul and ended up getting those upgrades that were gated by WIN X AMOUNT OF TIMES and everything unlocks. Categories don't mean anything.
Some upgrades are gated by your player level, however.
so that's how you've raced ahead on the crew leaderboards for races ;)