What spark plugs for supercharged LT1?
I started having trouble ~9 psi with my Vortech LT1 and an MSD 6AL fixed my spark problems. So I always use an MSD and my experience has been to gap ~.035" with stock heat range.
Others change heat range, but my experience with both turbo and sc is run an MSD and as your boost goes above say 6 psi start closing your gap with ~.035" the least gap you run.
I recommend the 6AL because that way you can progress to a 2 step and significantly improve your launch
Good luck
A friend runs the NGK TR55 plug I don't like gapping them, but he has had great luck with them he is running 22 psi with MSD coil and 6AL box and has had no problems. As I said the plug is at most 5% of the ignition problem with boost get an MSD coil and box and you won't be fighting ignition problems.
If you stick with stock ignition and an MSD coil you will be chasing your tail. I have been there and done that and I am trying to help keep you from having those problems.
Good luck
Like I said until you go alot higher boost the plug is not the biggest part of the problem. Get any plug and tighten gap ~.005 for each 5 psi of boost is a swag. Once you go above 5 psi get the MSD coil above 6 or 7 get an MSD box (6AL)
Good luck


