Good build for towing and gas milage?

I am looking to buy an '85 3/4 ton chevy pickup for my towing and November-March driving needs. It's clean, straight, the price is dirt cheap. The bad part is the anemic, 150k mile 305 SBC under the hood.

As an alternative to spending alot of $$$ for a new motor, I know of a '76 Electra locally that is rusted way beyond repair, but has a solid driveline (455-4/th400) with about 80k on the clock.

Even tho it's the dreaded '76 engine, I figure it's gotta have more TQ than the 305 chevy, and the block would make a great core for a future build. Also, since the 455 motor is fully outfitted with emissions gear, it will pass the new emissions regs that come into effect next month here. It's just a visual check looking for an AIR pump, EGR, PCV, charcoal canister, cat. converter, and a gas cap check.

The major issues I'm wondering about are :

1) Is it possible to get any decent gas milage out of the '76 motor as-is? The truck has a 700-r4 and 3.73's, so I figure highway milage should be reasonable, but I plan to use this for my work commute though and that includes a mix of back roads and city driving.

2) What would be the best combo to use at rebuild time? (cam, heads, CR, etc) I would need to keep the '76 intake because it has the AIR pump hookup on it. The pump doesn't actually have to work, it just needs to look like it does to the inspecting mechainic, i.e. belt installed and hoses connected. I also want a build that will run on 87 octane gas.

Thanks!!!

 

BUICK TRUCK

I had a 81 chev 1/2t 74 455, 260 comp cam, th400 3.08 gears, 15" tires = 18 mpg and a towing machine it was! And it was an easy install. My neighbour liked like my truck so much he got me to convert his 82 3/4t to buick power, 1970 455/370hp 268 comp cam,th400, 3.42 gears, 16" tires, It hated the 4.10's it was above peak torque and hard on fuel.454, 460, 440 all like 4.10's. But not the 455. The 700 trans will be unreliable in that application big torque, heavy truck, towing= broken input shaft. The input shaft is small and has oil holes drilled up the middle.Chris

 

I had a 76 Electra with the 455 that I towed a 24' Sea Ray. Comined weight of car and boat/trailer was 11000lbs plus gear and beer. With the motor completely stock, AND the 2.56 posi rear it towed that load quite well. Then I switched the rear end to a 3.08 posi out of a 71 Catalina, it woke it up a bit, but the big thing was that engine, even with the crappy stock 7.9 to 1 comp ratio it was a torque monster. It never ran hot, or burned oil. Wish I still had that car, or at least the 455:beer
My neighbors brother in-law has a beat up white Chev 1 ton crew cab dually that has a 70 455, he runs it at Norwalk Raceway for the Buick Race weekend, I think he's running in the 13's. He scours the yards around here and buys up all the Buick 350 and 455 motors he can, cool guy:beer

 

a different "twist".

LDPosse;

When you rebuild for towing, I would make sure to use the 3/4 grooved main bearings. I would wonder about using full grooved bearings with a constant load. Ask one of the Dr.s.

 

Re: BUICK TRUCK

Is that highway or combined MPG? Sounds like a nice combo!

Does stock include all the emissions gear still intact and functional?

Thanks for the input, guys!