Go with the ac delco plugs - thats what is in there now if they have never been changed from the factory. Gap the plugs at .040 and you will be fine. Check with what autozone's computer says for gap to back refernece.

Wires, go with whatever...ive used the duralast ones from autozone and never have issues with them.

Get a gap tool at autozone - they are like 2 bucks or something

Dont do the TB bypass....unless you want to in the summer months - its an easy enough mod to change it back and forth for summer/winter (couple of 1/4" hose clamps. But i wouldnt run the bypass with the winter.

 

if your misfiring at 55, its not the gap causing it. usually bad wires or fuel related. every ls based vehicle i have owned has been gapped to 55 without issues.

 

So, is there any performance or MPG pros and cons to 35 vs 40 vs 55 vs 60?

 

imo the only reason to lower the gap past recommendation is if you have some kinda power adder, or internal mods like heads/cams/etc. our engines produce a lot of spark output with the coil per cylinder setup, they can handle putting out a hot spark with a large gap. the larger the gap, the more spark that is exposed to the combustion chamber which allows it to burn more air/fuel. however the larger the gap gets, the weaker the spark gets and a chance of misfire comes into play so theres a limit to how big you can go. on the other hand, you have to worry about spark blowout. this happens when your cramming tons of air/fuel in the cylinder and the weaker spark isnt strong enough to ignite it all. so we then decrease the gap causing a much stronger spark. so for every vehicle and configuration there is a sweet spot perfect gap. if it were me i would just set it at 55 or 50 and call it good.
there should be a spark gap sticky somewhere in the boards that tells you what gap to use at each mod level if you search for it. may be on ls1tech.

 

oh another tip, a 1/2" wrench with a 1/2" to 3/8" adapter and a 3/8" spark plug socket works best on the number 8 plug. its like the perfect length and will not need any swivel extensions with this.

 

I run NGK TR55's gapped .055 on 91 octane with as much as 31 degrees of totally timing being delivered and have no KR or misfires.