With the mods I have and a 150 shot I am having very pour traction on my street tires. I have 18x10.5" rims in the rear and was thinking about getting the nitto drag radials (NT-555R) size 305-45-18, but these are a taller tire. I run the NT-555, 285-35-18's now. would this tire give me enough bite?

 

They will be taller. But enough bite for a 150 shot don't know.
I would add some LCA relocation brackets. Drop the LCAs to the middle hole. They might help you out.

 

I have the relocation brackets and BMR LCA's on the lowest hole, would the middle hole work better?

 

the middle hole wont shock the tire as hard.
Plus the fact that 18" tires arent meant to hook up bolt on power levels in drag racing,let alone another 150 hit of nitrous.

You can try the nitto's,but i doubt you will get any 18" tire to hook when the nitrous is on.

 

thats what I needed to know, I'm just going to have to look around for some 16's with some drag radials. Someone told me you could get 15's on if you grind down the caliper, any truth to that?

 

Yes if you grind on the caliper enough,you can get 15's on the back.
The LS1's take more grinding then the LT1's.

 

You could go big bucks and get some 15" Bogarts. They fit with no grinding or spacers.

 

150 shot? Et Streets, 15" rims, heat them up good on a sticky track and call triple A when you break the rear end.