C1500 Cheyenne 4.3L 5 speed rwd:
06/96 date of manufacture
Two motor mount sets now tried and just not usable: holes off, don't contour well to the crossmember!
Have ordered a 3rd set, but am wondering what gives??
Is my truck different somehow or special or are replacement mounts just poorly made??

 

Don't know your reason for tackling engine mounts, but 2 questions come to mind.

Where are you purchasing the poor fitting mounts and what does the trans mount look like, (condition) ?

 

My '96 runs like a top but had multiple oil leaks, needed a new clutch soon, so I decided to pull the engine and bring everything up to date with new seals, gaskets, timing chain set, freeze plugs, wires, plugs, etc. And one motor mount was sheared so I ordered a set through Amazon. Can't use, similar but clearly not usable. So went to local auto parts store and purchased another set, made by FMP, whatever that is. And they were identical to the Amazon ones. So now I am awaiting the arrival of a set made by a different company but am paranoid that something is different on my truck model? And as you well know, replacing the mounts is difficult enough without additional BS challenges! Trans mount was in good condition.

 

You should take the old mounts with you to the parts store and make sure the ones they have match yours exactly.