Yes I made my old harness run the new the 5.3, with some changes to make it look good. It is very time consuming but your right. Not very hard. The first time is always the hardest. As far as the l33 aluminum block being better, I doubt there is really much difference. The weight is a nice factor and the heads are basically 243s so that's pretty good as well. I guess it all depends on your goals really.