Probably not. The focus throw on these lenses were never made for good manual focus, so it will be hard to manually focus the lens precisely, compared to a lens designed to be manually focused (like a Takumar 300mm F4, around $100~120). At least definitely not for sports or things where you need to continuously focus, even if stopped down heavily for drafting, panning, etc. 1/5th the price, definitely not. Maybe for $100? I wouldn't pay more than that though for something that needs to actually be focused to work. It would be a great cheap way to get a high quality astro lens for someone doing DSO work though. But certainly not for cars.
Considering you have a 200 F2.8L, the answer is hell no, because you can use a 1.4x TC and have a 280mm F4 lens, which is nearly literally the same thing, with autofocus, and it's still very sharp wide open even if you needed it to be, and takes up less space and is universally more useful and versatile.