CompSyn, could you shoot a picture of the other side of the original gasket at the slot?

Here you go...

Pic looks like a round hole on left and a slot, also maybe block had the hourglass openings not just a single round hole, or is it an optical illusion. Trying to figure out if narrow slots were designed for hourglass blocks. Can confirm max wedge also were stock with .375 gasket

I have been chasing the cause of my 440 overheating problem here.....(https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2509662/1.html)

.....and for a couple reasons, I've convinced myself that it had to be the head gaskets. I've been through all the normal stuff (180 t-stat, no t-stat, radiator check, installed spring in lower radiator hose, new coolant, new water pump, checked engine timing, new coolant temp sensor, different temp gauges (2), installed clutched fan (had a fixed fan when I got it), etc and nothing has helped. Also, the upper radiator hose barely has any coolant flowing through it; my survivor 69 Charger with completely original 383 has much more pressure in the upper radiator hose.

I pulled the heads this morning and the saw a couple things. 7 or 8 pistons were kissed at one time or another.....but anyway, the cooling slots seemed suspect. They look way too small. What do you think-could this be the source of my problems? And does anyone have pictures of what the slots would look like? I've read that they were much wider on the original head gaskets. If anyone has modified the slots, does anyone have any pictures? Thanks

I can't see the pictures but the size of the slots are not your problem , there are thousands of big block mopars out there with the same head gaskets.

I have a friend that had a similar issue that nothing he did would fix, his engine was also .060 over ....

I have to agree with John. I think at least part of the over heating issue you have is your .060 over bore. That much bore usually makes a 440 engine run on the warm side. Boring a 440 motor.060 over is great for a race engine that only gets run for a few minutes at a time, but not a street driven car. Is this a numbers matching motor to your car?

It is not the numbers matching block. I was just getting ready to sell the car and I can't sell it with an overheating issue.

My 440 is .080 over, no cooling issues at all. Its not the overbore, we have lots of customers cars at .060 engines and no issues. One engine we took apart due to overheating that was "rebuilt" had lots of crud in waterjacket but big issue was old core plugs pushed into the water jacket and left there! Originals are thinner cup shape and one made it up to passage closer to pump, very poor flow resulted.
Some aftermarket pumps have very small impellers, some others are 1/2" away from the curved surface in the housing! Is there a big chunk of crud blocking passages in the radiator?
Deleting the thermostat without some type of restricter nearly always overheats.

My 440 is .080 over, no cooling issues at all. Its not the overbore, we have lots of customers cars at .060 engines and no issues. One engine we took apart due to overheating that was "rebuilt" had lots of crud in waterjacket but big issue was old core plugs pushed into the water jacket and left there! Originals are thinner cup shape and one made it up to passage closer to pump, very poor flow resulted.
Some aftermarket pumps have very small impellers, some others are 1/2" away from the curved surface in the housing! Is there a big chunk of crud blocking passages in the radiator?
Deleting the thermostat without some type of restricter nearly always overheats.