What is the difference on the 188 and 088 heads

I believe that the 188 head was the last revision of the gen 4 series of heads. The 088 was introduced early 90's on the genV motors and can't be used on the genIV without the risk of water leaking into the lifter valley. The Gen 6 heads were reworked to allow bolt on to the gen IV with the correct fel pro gasket set