I have to admit, I've rarely seen a 4c process screen print job that didn't look cheap to me unless the printer custom mixed the four colors. And if it did look good off the press, the first wash usually killed it with fibrillation --- where the "hair" of the shirt breaks from the ink and makes it looked washed out.
Then too, I'd think there would be a compromise with the blues trying to get a balance between the chrome blue and an eye popper blue on the Mustang. Same with the red trying to get the Corvair red to keep from looking pastey and the Pontiac red fairly deep without a white.
This would be an awesome 8c.
White
Fluo Blue
Bright friggin' Yellow
My favorite custom mix Fluo bright friggin' Red
Deep Ford Racing Blue
Dark Black
Pinstripe Gold - maybe a mixed metallic
Highlight White
oooooooooooooo baby, that'd be sharp and print on any color T-shirt. What's your budget? and, and, 45 maaaaaaaaayybe a 55 line screen to get some good color. 220 mesh @ 25 Newtons. ...150 mesh on the pinstripe. buuuut I don't print anymore.
It's a minimum 5 color - 4c process with a crush white on light shirts. The white will be the most important separation to pull of a spectacular print!
The best contact that I remember in the business for that would be Coudray Graphics --- Outstunning separation work!
If you don't have time to explore other options or referrals from s101, Call them for a recommendation on how the art could be sep'd and a referral to a printer near you.
NetSeps
Best