[rpoz11]

"My question: was the ZL1 option available without the L88?"

I doubt it,... if you look at what every ZL1 came with internally, you'll see GM's intentions. It was a short lived run, and I believe had only one purpose!!!!
The de-tuned version played with by GM , to me, has not ever shown what was run internally, though considered, never made it to the showroom nor production.

So for your answer, NO!