Will this fit in my 1973 Comet

Size-wise, the Boss is like a 302 block with 351c heads.
Very nice fit compared to a 351.

The only headers that I know of are from Tubular.
They look just like their 351c headers, Tubular sent me a set by accident when I ordered my 351c headers. Drove me nutz for a while trying to figure out why all the tubes seemed too short. Finally realized what was wrong, and Tubular fixed the issue with no questions. There could be other headers that fit, but I don't know of any myself.

I read an article from the early 70s on a Boss 302 swapped into a Maverick, and they complained about the high rpm nature of the engine. They noted that they were using 4.11 gears, but had a close ratio toploader behind it. They felt, and I agree that a wide ratio toploader would cure some of the drivability issue. Just throwing that out incase you are considering putting anything but a wide ratio 4 or 5 speed behind that engine. Any tranny with a first gear higher than 2.78:1 might be lacking is my point.

 

OH That's right LOL Yep I kept walking by it, I hope I didn't spill too much drool on that engine bay.

 

I hope he takes it to the route 66 show this month! im dying to see that car in person

 

its a beautiful car with a lot of custom details, i also suspect he has a stealth technology camera interference device onboard as all three of my pics of it are blurry, yet all the others i took that day came out fine....