Always check the gap!! I have worked in may a parts store and have droped may a spark plug. The gap should be correct out of the box but the idiots ( ie. me) who ship and stock the parts may have messed them up!
dOOd, the spark plugs have a protective card board tube that protects the tip...you could drop it all day and it shouldnt affect the gap,,,STILL each vehicle that uses the same plug may and do have a different gap..depending on the electronics..i would never just stick a plug in a head with out first checking the gap...
heres an example out of my sevice manual for my s-10 pick-up..2.0 engine rv12yc plug..gap 0.035in
the 2.8 uses the same plug but has a 0.045 gap..
the 2.5 and 4.3 engine share the same rv15yc plug, but the gaps are 0.060 and 0.035in !!! see what i mean..??