I have a 01 Rcsb nbs that originally was a 4.3. I swapped in a 5.3 a while back and now am looking to upgrade to a 4l80. I found a good 4l80 out of a 99 obs but I havent found any info on whether or not it will swap in. What year 4l80 do you look for? I know I will need harness mod, crossmemeber mod, etc I just need to know what year 4l80 are the same, What years are different. Thanks