At first thx at all

It is a 400 er Small Block no Big Block.
Yes I have the Original Heads .But I read that Chevy Heads before 1974 are not so good.
I can get some used old Heads from a 350 for a low Price.
Some Power in my Engine will be fine but the important thing is to drive it every Day without Problems. Gas is very Expansive (like everything in Germany) and it will be fine to ride with low Octane