I believe, based on what I (think I) know, that the difference between the L88 and the ZL1 was the composition of the block. In other words, when the ZL1 made the scene, the L88 was now using the open chambered head design, so, there would have been no difference there. I've read over the years reports that camshaft specs were different, but, that may or may not be the case.
The reason, I believe, for developing the open chambered design was ostensibly to create better burning of hydrocarbons. The end result was a better breathing engine that although had a reduction in compression (12.5/1 to 12.0/1), made more power. The redesigned piston (see PIC) simply reduced the 'squish' area between the piston and the cylinder head. Again, the result was better breathing (more power) with less pollutants escaping unburned.
Regards,
Mark