Tips for better fuel economy

I'm not really impressed by what I'm reading about the fuel mileage with the carbed trucks.My fuel injected B2200 is far better on fuel.My last fill up (mostly highway) was 34 MPG.It has the the auto.trans with overdrive but this truck for various reasons is basically on it's last legs.It has 380,000 km.'s(232,000 miles)smokes alot on cold starts,very rusted frame,upper control arm shaft is in very poor condition,etc.
It did get new plugs,fuel filter,a rotor and cap just a few month's back though.
Please note that I'm in Canada and MPG is in imperial gallons and not U.S. gallons.Imperial is slightly larger measure than U.S. but I attribute better fuel mileage to fuel injection as opposed to carb.
I wouldn't drive a small truck that only gets 20 MPG.What would be the point?

My 86 b2000 w/209000 miles gets around 23 mpg. She is bone stock with the dizzy retarded almost all the way. It also depends on your rim/tire combo im running stock chrome mazdas(the chrome is more aerodynamic) lol

See now my 84 b2000 got 37 average on my trip from montana to idaho and that was including the few times i left it idle while going into the gas stations. Its stock with a overhaul 40k back and my sparkplugs are showing I'm running rich still. Of course i was doing 55-60 the whole way which is what the truck is meant to do.

Don't want to sound like a d*ck, but there's no way you're getting 37MPG.

Ok I have owned my 87b2200 since brand new.My average for city was 20-22 depending on my (manual driving) but 20 is point.Hwy best was 29mpg but typically less like 24-26 at 65mph.Normal tune ups run accel wires,ngk plugs,accel coil,replacing charge air filters in air cleaner,good 02 sensor,clean carb,and clean egr,and no restrictions in exhaust like pre cat below exh man cleaned out,good cat convertor etc.As for e85 it actually produces less energy than normal fuel,so you will burn more.Try doing 60 hwy,less quick starts,less stop and go (auto) only to keep a good #.Idk what else to suggest but 20 mpg is solid for the b2,b22 overall stock.Unless I missed something or wrong may others add/correct me if need be.Tired is kicking in so bare with me.

My 89' B2200 w/5sp, 165k, is now getting 23-24 mpg town, 26-27 highway. I did a weber conversion, ripped out all emmissions, no cats, and installed headers. I also drive for economy so guess that helps. I did all this work, because my truck was running horribly, stalling at idle, stumbling at all speeds. Couldn't find the problem, so decided to start with the carb, replaced it and it ran better, but still stalling at idle, and slight stumble. Punched out the rear cat next, which made it run a bit better. Took off the exhaust manifold to check the can cat, and sure enough, it had broken into pieces and had falled down into the bottom of the can and was plugging the exhaust pipe. Back pressure was causing all my problems and the engine running lean due to exhaust back pressure. Put headers on it rather than pay for new cats. Wish I would have figured out the problem before changing everything. But, it does run a hell of a lot better with a weber and headers!! Before I got the exhaust pipe made and connected to the muffler, I had to drive 300mi. roundtrip to Portland, Oregon for an important meeting, I had to go, so drove the whole trip with the headers uncorked. Noisy as hell and had to baby the throttle in town once I got off the freeway. But anyway, made it without getting pulled over by a cop, and I checked my mileage just for that trip, and got 30 mpg with the headers open. So much for the restriction of a mufflered system.