I need advice on motor mounts. Anybody with experience would be greatly appreciated.

The polylocks are designed to 'lock' in place, they will not pull apart, but they will slide apart, if that makes sense.

I could see the poly stretching and the motor got lower on the passenger side.

Got them directly from Schumacher. Their customer service was very good, replaced them twice, so three sets.
They asked me to build a heat shield, done, two different versions, but also agreed one should not be needed at all, especially on the driver's side. It is clearly not caused by heat, driver mount is way forward of the exhaust.

They wanted a torque strap installed, original bb car so theirs was not an option. I told them I put a chain on it, and the second round I put a bolt right through the driver's side mount. Passenger side still failed.
They would only warranty if I had their headers, I did from the beginning.

Gave up, bought their powder coated brackets with rubber mounts, passenger side bracket bent. I put it in my vise, bent it back with ease, didn't even hurt the powder coat.
I put my original bracket in the vise, couldn't bend it at all.

I did everything possible, mounts failed, engine leaned to passenger side permanently each time, and then their new bracket bent.

They don't melt, it's not related to heat, they slide apart.

People tell me all the time, they have them, no issues, however when I ask if they actually looked at them they say no.