I don't think these new motor mounts at O'Reilys, Napa or other stores even meet manufactures specifications.
and they call these OEM replacement parts, I can see a repop part not working, but an OEM?
These new mounts have to have the studs shortened so they don't put a hole in the block,
and the rubber is way too soft as I could probably pull them apart easily if I wanted to.
I purchased a set at the local parts store for less then $7.00 each. If I remember correctly, Moogs used to cost about $15. to $20 each 40 years ago.
I don't mind paying for a quality part. especially when a failure could result in a damaged hood, air cleaner, fan shroud or radiator.
Maybe I will just use my 40 year old Moogs.
I've heard the Poly mounts and the so called "Bolt Thru" mounts cause a lot of vibration for a street driven restoration.