When searching either online or at an auto parts store, search for either P30 or P32 where it asks for the model number.
For instance 1987 Chevrolet P30 (or P32) rather than
1987 Chevrolet Suburban.
I've had a few parts guys look at me funny when I say P30 for the model. I just smile and say 'Trust me on this one - look it up'. Then the next thing I hear is "wow, there it is".
Obviously some parts guys have heard of it before, but not all of them.