Don't forget that the btu rating is per pound of fuel. Per pound of air you burn more e85. To compare the power output you need to correct for this, a stoiciometric mix of e85 and air is 9.765:1 (http://ethanolpro.tripod.com/id213.html), petrol/ gasoline is 14.7:1 meaning you burn 14.7/9.765 times more e85 (1.5 times more). To compare the BTU rating you need to multiply the e85 btu value by this factor i.e.;

115,000 x 1.5 = 173,118

A decent increase, add to this that it cools the intake and hence you get a little more air and you get an increase in power! (That's assuming the engine is properly tuned for it.)

Edit: Fuel consumption will go up, economy on the other hand depends on the price of each fuel. Switching straight over with no change to the carbies it may be too lean to run properly if at all. Cold starting also worse, even with e10.

There are many "car guys" running E85 on vintage cars, even a few on the Datsun 1200. Here is some info I gathered from previous discussions.

MODS
The only mod needed is a carburetor with much larger jets. It is optional about the corrosion-resistant fuel lines, metal parts and rubber parts, etc. It also seems you don't need a higher-capacity fuel pump or larger diameter lines for a plain conversion. But you would need it if you plan on making more power.

POWER
A straight conversion of the A12 to E85 will lose about 30% power and fuel economy.

ECONOMY
As E85 is a bit less expensive than gasoline in most places, it effectively costs only a little bit more per mile.

POTENTIAL
The 'effective' Octane Rating of E85 looks to be quite promising. A raise from 9.0 to 12.0 will recover the missing power. Higher compression ratios reportedly work with today's AUS E85 and USA E85, at which levels you make more power than you started with.

Turbo engines are even easier. Just raise the boost up higher with the E85.

E-85 requires much more compression on a non-ECM/PCM controlled engine.

FYI,
Pure Gasoline has 115,000 BTU per US Gal
Ethanol has about 76,000 BTU's per US Gal

On Carb/non ECM vehicles, the A/F ratio has to be richer by about 30% or more.
E-85 was designed for Flex/Fuel Vehicles.

Note Alcohol Dragsters must build Massive Engine Heat or they have icing in the intake, then a massive BOG as the engine drops power.

Run it out, siphon it out, and Hope it don't erode your rubber components in the fuel system.

I think Brazil uses Ethanol as a primary fuel, but they can produce it cheaply and modify the vehicles to operate properly on it.

As the car sits I run 93oct and the car runs super smooth but was just wondering what was involved other than jetting the carb.

So nobody runs on E85 here?

You'd need to at least rejet your carbs to flow more fuel, something shy of 2x as much fuel. If you're up for that and a good tuning then you should see a modest increase in power from what I've read. It'll run cooler and cleaner on e85.

If you have pre-ignition or detonation problems switching to e85 with a fresh tune might fix that if the problem is too much compression, much like switching to a higher octane petrol (gasoline).

Edit: 75% richer. From what I've read e85 does not pose any significant corrosion problem. As with any fuel system keep it clean.