New heads!

More to the point, the valves are canted, not in line. The differences are pretty obvious.

 

Are these heads worth anything? I'm not going to be building a monster of an engine. Mostly something to have fun and street race with.
Mostly a torquey traffic light scooter. And I know gt40 heads are an option, but I heard these D0s have more potential

 

Considering the deck surface thickness is more than sixty thou, you can shave them, put a decent valve setup in them, drop them onto a decent shortblock with a good cam and selected pistons. BTW, I have the oil pan and dipstick tube/dipstick to put a 351W into a Panther platform.

 

Oh nice, where did you score it?

 

Babe's donor car was a '79 Grand Marquis. Since I had to change to a front-sump pan, I wanted to keep those parts in case I did something with another 351W, or if someone else wanted to.

 

Actually, those deposits don't look worrisome. Most of the time, I've seen much worse. Muriatic acid is for garage floors. I'd hesitate pouring it into the cooling system.
Those spark plug threads don't look like the healthiest, though

Ever thought about attending an evening cooking class, instead, judging by what you're preparing in your kitchen? When you're using ingredients like Gorilla Glue and STP, it should not wonder anyone that you're seeing massive calcium scale and Cleveland heads:

 

Yeah yeah very fuhnny

That std filter is one my dad picked up for his explorer. I don't even touch that brand, I use motorcraft most of the time.
As to the gorilla gloo, what else am I supposed to huff, I don't have any other glues around right now.

 

The C9 and D0 heads were considered one of the better stock SBF heads for a while. Modern heads can outperform them, but they are still respectable. I have a set of D0's on the 351 in my Crown Vic. They do not use the pedestal mount rocker that is common on all later model SBF heads. There was also something about the older heads having less or more intake manifold bolts (it has been 100 years since I was into this), but it isn't an issue using a later intake with them. They should have 60cc chambers which was good for a decent bump in compression over the E5's that were on my engine. They should be a decent upgrade over the E6 heads on your engine if they are in decent shape and don't require a ton of work. They do require the older larger spark plugs so you will have to dig around and determine what plugs would work best for you.