What is the standard on the most compression

Being a Hemi (needed information that was left out of the first post, duhhhhh), you might can get by. There's a guy over on The Hamb with a first gen 392 Hemi with 13.5:1 and runs 93 octane. The Hemi chamber (especially the early Hemi) has superior anti detonation proporties. You can "try". I would massage all of the sharp edges off the pistons and smooth the chambers as much as possible. Anything such as sharp edges that could provide a hot spot for detonation to begin should eliminated. You'll have better success with a Hemi than anything else......but I still think for best results you'll need to spike it with race gas.