Ok, as i have been posting, i had a fire and need to rebuild my 74.  This car i drove an average of 18,300 miles a year, basically every chance i could with no rain in sight. 
   The motor now was the original 350.   No matter what, i am going to pull out that, strip it down and keep it, in case i ever desire to sell it, i have a numbers matching car.
   Going into the car, i am curious.  MPG is an important factor.  (If i want a hot rod, thats what the Red Vette is for)  I am thinking of going with a 305, 4 barrel, so that it still looks stock, but i am hoping to get good economy with decent performance.  Basically what they had in the early 80's Vettes.
    My question: what kind of mileage improvements did they get with that motor?  Does anybody here have one that is still stock, what is your mileage? for that factor, what kind of mileage are people getting in their C3?  Before the fire, i got an average of 16 freeway, 12 combined, city was this scary sucking sound.  I kinda enjoyed the take offs.
   I am switching the rear gears while i have it down.

The best thing to do for better milage is to put an overdrive transmission in there. It will put you into the twenties on the hyway. My '82 has the 700R4 trans with a 3.55 rear and I get about 24 on trips. The '82 also has fuel injection which helps a lot also.

Fuel economy...what's that????

My '78 L82 isn't too bad...about 15-16 mpg. The '69 427/435 with the L88 cam and 4.11 rear?   Surely you jest...and I'll stop calling you Shirley! Maybe it gets 6 mpg...about 125 miles to a tank.

I was gonna put a Keisler 5-speed in it about 18 months ago until I ended up in the hospital for a week. Had to cancel those plans to pay the bills. It's numbers matching so I'll just leave it as is.

I still have the old lead engine in mine and use premium gas, plus a lead additive.  It's the 350/350. The only change is the distributor, edelbrock manifold and edelbrock carb (600) and I'm gettin' 20 mpg.  At least that's what I got going to PF from Texas and back.  I still have the original manifold, distributor and Q-Jet.

I haven't checked mine since the vacuum leak was fixed.  Talk about a giant sucking sound  I was gettin' around 10 with the leak.

I talked to Adams' Apple (Joel) about a 700R4.  It has an overdrive, it'll fit my '80 and will be what I add to get the mileage up.  You're lookin around $1500 at www.phoenixtrans.com.  They're from Weatherford TX and if you bring it to 'em, they'll match it to your gear system and install in about two days.  Otherwise, they'll match it, ship it and let you install it.

Good luck!

All the original '82's have auto with overdrive with two different rear axles get from 15 (city) to 25 (highway) on 87 octane.    

Wow, I just barely get 17MPG on the highway with my 3.55 gear and 200-4R Overdrive trans. I guess I better start working on the carb, a little more tuning is in order.

I've got a TKO-600 w/3:70 gears & a 454HO that puts out about 500hp & I get 14-16 on the highway & 10-12 around town if I drive easy. If I put my foot in it I keep looking for gas stations all day.

Before the odometer quit working "The Toy" was getting in the upper teens out on the highway (350/300hp w/4-speed manual).  It also needs some tuning and carb adjusting so it might do a little better after that.