Here's my walkthrough of the third list for when you get there:
Blade: Very easy. Anywhere in the Los Santos ghetto. Or the San Fierro docklands. Or most of the backcountry. They're everywhere.
Freeway: pretty easy. The freeway between the Garver bridge and southern Las Venturas seems to have a disproportionate number of them. You'll probably find one parked in one of the redneck towns if you spend a minute or two wandering around.
Mesa: I have no idea. It looks like a Jeep, if you haven't driven one yet.
ZR 350: Venturas strip, bottom of the Vinewood hills, downtown San Fierro
Euros: WHEN (not before, not after) you unlock this list, this car will spawn under the sphinx at the Camel's Toe on the the Las Venturas strip. This is the only place and only time it will ever appear, so if you don't want to pay to import one later, grab one now.
Banshee: Next to the gym in SF
Super GT: I think it was required that you bronze driving school to get to get the import list unlocked to begin with. So this should be sitting outside.
Journey: The big RV. The big long highway around the outside of the SF island should be infested with them. If not, there's a spawn on top of Mt. Chiliad.
Huntley: It's a Land Rover, try Prickle Pine.
BF Injection: I think there's one that spawns on the beach near the country club in SF. If not, try crusing any beach district. If you get desperate, there's a spawn by the snake farm near the Verdant Medows airstrip.
I'll add a couple of things and make it easier for you...
Here's my walkthrough of the third list for when you get there:
Blade: In El Corona, there's a big housing area, with a road squaring around. Off this road, there's a road that leads to a dead end, I think it's possible to buy a house here. In one of the driveways, there is a Blade parked.
Freeway: Head out to the Desert or Country. There's always plenty of Freeways, Sanchez's and Wayfarers.
Mesa: At the base of Mount Chiliad. It's parked on a fairly decent-sized area of dirt, not fair up from where the sanchez and mountain bike are, with the sort of mountain-bike racing thing is.
ZR 350: Like most nice looking cars, head around The Venturas Strip, Prickle Pine, Downtown Los Santos, Downtown San Fierro or Calton Heights. Not hard to find.
Euros: Spawns underneath the Sphinx at the Camel's Toe.
Banshee: Next to the gym in San Fierro.
Super GT: Get all Bronze in the Driving School and one will constantly spawn outside in the parking lot.
Journey: On top of Mount Chiliad. Not too hard to drive it down, if you're patient and drive at a reasonable speed, you can get it down without damaging it, which means more money.
Huntley: This only happens while you've unlocked the third list and before you've taken one to Import/Export, but if you get all Gold in Driving School, the game will glitch and instead of the hotrod spawning there, the Huntley will spawn in it's place. I'm not sure if this works when you have not got all Golds.
BF Injection: If you drive around the housing areas of the desert or Las Venturas, you should be able to find one after a while. Probably the most difficult to find on this list.