330 LC 2 barrel. Has been running from the original owner for eyars with 87-89. Do you think if I fill it after she gets close to E with 93-94 it will make a big difference, what could I expect. Thanks for you insight.

 

It will not make a big difference, and you can expect to spend more money on fuel. If properly tuned, 8.5 - 9.0 compression ratio cars will run on almost anything.

 

Since it's a low compression motor, it should run on regular if properly set up and tuned.
Maybe not 87-regular, but certainly 89-regular. I can't see a reason to run it on more than 91, even if you want a margin of "safety."

Remember, these engines were not spec'ed to run retarded from the factory - they were supposed to run with a correct amount of advance, so advancing it more and using premium probably won't get you much , if anything.

- Eric