Be sure to check for bent rods. Also check the block deck and heads to see of they are flat.

Detonation
 

After an expensive rebuild of my detonated 327 my builder/machine shop figured out the timing mark on my larger harmonic balancer from a 350 didn't jive with my 327. At TDC the mark was out 14 degrees so he scribed a new correct mark on my balancer.
This wasn't the first motor I lost to a bad timing mark. The first build didn't have forged pistons so it was toast after 40 miles. The 2nd build lasted 700 miles...fingers crossed for the 3rd build!

I'd be looking for the correct balancer for the 327. They were much thinner and lighter. That 8" balancer might be stressing the crankshaft.

I would like to know which cylinders had coolant. I’d also like to know what valves were damaged, and a lot pictures.

L79's, L76's, and L84's all had 8" balancers

Same engine builder?

I always check the timing mark on a engine that I'm building using a piston stop before putting the heads on. I never trust it until I verify that it's correct. I even verify TDC on a running engine that someone brings to me for tuning using a piston stop in the spark plug hole.

The guywho did the machining did the reassemble this time.

To Freddie's point, I don't know of an engine builder who does a complete build, (including timing cover and balancer) that would not confirm TDC. With the variations in timing covers and balancers, there is no way properly know where the timing is at.

On a different note, did you hear this thing detonating?

Sorry to hear you are struggling like this. After everything you have shared, I believe the time has come for you to find a different engine builder.

I do the same, I think that's one of the most overlooked things on an engine.