My most sincere apologizes for the delay in response!
I've been sidetracked from the forum by work (my regular job!) and caring for my wife recuperating from major back surgery!
I'm hoping this reply isn't too late for you to capitalize on you pending sale!
From your Engine Casting number, 60066036, this is definitely a 350 (5.7L) CID Hecho en Mexico crate engine.
Interestingly, the detailed info on crate engines is sparse and difficult to retrieve!
I think you've experienced that!
You mention you have already attempted my first suggestion; 'note the Engine Assembly Code and the Block Casting Number, stop by the Parts Department of a large Chevy Dealer, see if they can look up the references on the engine and give you the HP rating, etc.
General information;
The engine block doesn't control the Horse Power output!
The internal components do.
For example, the pistons and cam have the most internal effect on the Horse Power output of an engine.
The External Components, Intake Manifold, intake device (Single Point (TBI) or Multi-Point fuel injection, or carburetor), Heads, exhaust manifolds and exhaust system also greatly effect the engines Horse Power output.
Now, from my extensive research on the Block Casting Number and Engine Assembly Code from the engine casting and stampings you posted, I've found the following;
8.5:1 Compression ratio, cr, cast dished pistons, hydraulic flat tappet cam with .383I/.401E lift and 112 deg lobe separation, cast iron 76 cc cylinder heads, 4qt. oil pan.
This is the 260 HP version of this engine.
There wasn't a 250 HP version of this engine.
If the engine is the high output version (300 HP), it has everything as above (including the Engine Assembly Code, after all, remember, this was assembled in Mexico), except the cam is .222/.222 deg dur. at .050 lift, .450I/.460E lift.
To determine the engine Horse Power, it will be necessary to check the cam.
A simple way to check the cam; pull a valve cover, set up an indicator on an Intake valve tappet (at the valve stem end) and turn the engine through to cycle the valve up and down, measure the travel. (a magnetic stand and 1" travel indicator can be bought at Harbor Freight Tools for about $25 +tax, total cost) (one could even use a dial indicator to measure the valve travel. A 6" one is on sale at Harbor Freight Tools currently, for $10)
Is the Intake Valve travel 0.383" (=260 HP), or 0.450" (=300 hP)?
So, the reality of the situation is; in this case, the cam is the deciding factor in what the HP output of this engine is, regardless of the casting numbers or stamping numbers.
Lastly, I understand why the Fulton Chevrolet Dealership closed;
You posted, "the codes from the block are 10066036 and front 1M0613 6VP. My receipt says 10067353, ENGLM1LS9."
The engine stamping and casting numbers and the receipt numbers are completely different!
They describe two completely different engines!!
My question for the prospective customer you have is; "What are you buying, the engine, or the receipt!??"
The numbers in cast and stamped into the engine block are what he's buying!
Measure the cam travel to decide what the engines HP output is and go from there.
I hope some of this helps!
Again, I apologize for the delay in response.
Please don't be a stranger to the forum, stop by from time to time and let's know what the final decision is on your engine!
