how difficult would this be to do? ne major problems i would run in to. ne difference in performance, and would my ls IM fit? bent valves on my old ls head so need a fix, came accross a b20z head for almost nothing.
thanks in advance

 

Aren't the b20 and b18b heads the same? It should be as simple as your ordinary head swap. And yes your b18 IM will work on the b20 head.