so on a lightly modified engine does the plug wire size really make a difference? would there be any difference from the cheapest to the most expensive wires? if so what is it?

don't buy the cheapest. They will suck a lot of juice out of your ignition system. Just go with some kind of stock replacment, or any other nice 8mm or 8.5mm wire.

I have a 500HP carbed motor and I am running 8.5mm MSD. Just depends how much $ u wanna dump on it. I got these cuz I needed to suctom fit them + i wanted some nice quality ones (also they are red and that was nice, haha)

well cheapest is usually stock replacement. and most of them are 7mm. for a lightly modded motor does it even make a difference?

Pending a definition of lightly modded, not really.

k&n filter, different cam and p&p 416 heads. everything else stock even exhaust manifolds

yeah those will be fine. Don't worry too much about little things like wires. There are a bunch of other things that have a better bet of causing problems. just chem the resistance with an Ohm meter. Then you really know what you are dealing with, no matter how many mm they are thick.

well i have to replace them now anyways. the #8 plug wire split and is arcing out the side of the wire. i just wasnt totally positive if a larger size plug wire would make a huge difference or not.

i always go with some of the cheaper (not cheapest) 8mm wires. i use accels. they seem to last a bit longer than the small ones, and my aftermarket coil did nothing until i got something to replace the 7mm suppressions...

even then, all it did was smooth out the idle and make it feel a little smoother at high RPM.

i like taylors 8.5mm custom fit wires the best though, i just won't spring for them since it's a (semi) disposable part and it seems like its a waste of money on my v6.