This is going to sound pathetic, but what is the best car to use in these races (Japanese Classic) in Beginner? The main reason is that it unlocks a photo location (I think), and it's the last one left for me to unlock I believe.
So, do you have to get the Toyota 7 in B-Spec? Gonna be hard, I haven't even bothered with B-Spec yet lol, and it's hard to find a fast Japanese car earlier than 1979.
If you are not in a rush, some old timers come every now and then @ UCD. they would be in the range ~ 30K to 500K, with those lower HP cars, you will be able to mod to a higher HP for an easy win.
As others have said, just about any old Japanese car you can find at the UCD can be tuned up to win this race. I believe I used a Nissan Bluebird with pretty light tuning. The competition here isn't really that stiff.
Alternate choices (that will be available to you long before you can win the Toyota 7 from an Extreme level B-Spec event) if you REALLY don't want to pay for something:
Dome Zero Concept '78 from the Supercar Nostalgia Cup Amateur level A-Spec series.
Honda S800 RSC Race Car '68 from golding the IB license tests.
If you're not bothering with B-Spec, you're missing out on some great free prize cars. You get a Shelby Cobra 427 & a Mazda Furai from a couple of the Amateur level races. These cars can then go on to win you a LOT of both A-Spec and B-Spec races. Including the Supercar Nostalgia Series I mentioned above.