Changed the plugs on a vette I just bought its a 2000 6spd has 96k miles
Anyways the plug gaps ranged from .68-.75 all looked descent but a huge plug gap.
I was getting a slight puttering when I was hitting 4k rpm almost like the car was hitting a small wall.
Changed the plugs and *knock on wood* so far everything is ok

 

I would say .040" to .060" maximum.

 

.060" is the standard gap for certain years . And other years .040" is the gap . When You buy the plugs go by the info on the little boxes and if not there then look it up online Google or a retailers site or call the place You bought them and ask . To answer You're orig question , anything more than a cpl thous. more than new specs is exessive . Sounds like a nice ride .