86 C10 AC Compressor O-Ring question

[Harmon]

Hey all,

I have an 86 C10 that was originally a 305 engine.  I am putting a new AC compressor on.  The new one has a different style O Ring connection on the back of the compressor. 

I am aware there are two types.  The one on the truck has the O Rings already in the compuressor while the new one does not.  My new one also did not come with any O-Rings. 

My question is does it matter what type of compressor goes in based on the O-Rings?
I am not totally sure if the old compressor is even the correct one for truck.  So how would I know which compressor would be best?

At a stand still, thanks for reading/helping.

[bd]

Post pics of the hose manifold and the pressure/suction ports on the back of both compressors, clearly showing the o-ring grooves and seats.