As others have already posted, cylinder pressure & cam overlap will dictate the CR teh engine's actually experiencing. Based on my fairly similar combo, I don't foresee much success with 87 unless you pull so much timing out of it that the MPG drops like a lead balloon. That said, I've been in that spot before, and I just "drive around it" as far as RPM/load/speed for the most part, but in some situations that's almost impossible to do.