For towing, I put in 92 and a can of Outlaw Octane booster. You wouldn't believe how well that makes the Vortec 5.7 run.
The octane booster that you buy in the autoparts store is a marketing scam really. When it says it raises the ocatane one point what it means is that it goes from 93.0 to 93.1 octane. This has been a big deal on the MR2 forum where we all have turbos and are looking for the highest octane possible.
Another thing worth noting is that if high octane gas isn't available or affordable, a good additive would be Tolulene. I think Tolulene is something like 120 or 130 Octane and can be found at your local paint store.
The 304 gets 12 gallons of premium(93) and 2 gallons of 110.
Just out of curiosity is the 110 leaded or unleaded. As far as I know the highest unleaded fuel available is 100 (I could be wrong). If it is leaded that is bad for your cats if you still have them and also not leagal for use on public roads.
As others have stated you only need the higheroctane if you are getting engine pinging/knock/detonation. Typically, this is more common in high compression and forced induction engines, though i see more and more new cars recommending 92 octane.
One question i have is what year did Jeep start installing knock sensors?
In my mr2 if you experience knock it will retard the timing so that it will still run safely. So you won't damage the motor by running the lower octane, but you will ruin your gas mileage and you will be down on power significantly.
Oh yeah, 87 in the Jeep @ $1.49/ gal (super cheap for California, I can't explain why, 4 months ago i was paying nearly $2.00/gal).
The MR2 gets the highest available, which in california is a wopping 91 octane @ $1.70/gal.
Another, option if the higher octane gas isn't available like here in california is water injection. It cools the charge air temperature, adds detonation prevention and steam cleans the cylinder walls.