I forget the actual diameter of my rear tires. I'm thinking around 28". It is a 255/55/18 BFG KDW. I had suggested doing the 411 swap to the tuner I am going with and with a few others who seem to know alot about these sort of things. All said the same thing, that because I am doing such a mild build, the blackbox can be tuned to work with my combination. Another thing with this truck is that it willbe put up for sale once I have completed it (it is apart for body work). All the parts going into this truck are parts that I had including a fresh 355 just sitting in the garage. I do not have a 411 pcm handy so if the tuner says I do not have to have it, I'll try running it without the swap. I am going to go ahead and put a little cam in though to replace the lt1 cam that is in it. I thought that I may drive it for a little while with that for sale sign in it so i had better give it a little get up and go to make it fun. Getn back to the cam selection, does the lsa of a cam affect the tune? I thought it would. One of the cams i am considering had a 108* lsa. It was in the 1000-5000 rpm range and cam company said it gave a noticable idle. Not a big cam at all, but with the lumpier idle maybe the tuner would change his mind about the 411 swap. I'll run it by him. If the 108*lsa dosen't work, there were also cams listed with a 110*,112*, & 114* lsa and all were close in size with the rpm ranges listed above. They also had cams listed with the same duration and lift numbers but with the different lsas. I really would like to have that noticable lumpy idle though.