[zdld17]

More likely Powerpack, early heads

 

[zdld17]

Small heads, chamber and valves. They will fit the 55 you have.

 

[zdld17]

I also just noticed that these heads have NO accesory mounting holes...what does this mean?
Are these heads worth selling?

Would they be OK with a 280h comp cam in a 8.5:1 motor?

No bolt holes means not accessories bolted to head like alt mount, AC braket. Most those brackets were hung on outside mounting holes like water pump and exhaust manifold mounts. Think you could do better .