11.5 isn't bad for a 350..... If you tow or haul anything with this truck, I'd stick to the small block. They're easy to work on and parts are everywhere. You can get a completely new one from your dealership for around $1300 (here), and it should bolt right up for years of reliability. I'm not sure how much, if any better the six cylinder's mileage will be, but you can count on a loss of performance if you go that route. Good luck.
Jay - Having had seven K series trucks in the last 15 years 11.5 mpg is not that bad. I currently have a 1987 V-10 4x4 that has a 5.7 and a 700-R4. I am currantly getting 15 mpg on the highway due to the overdrive, that includes running on 11.5x32 inch BFG tires. If you are running a standard 3 spd with overdrive your mileage would be around what you are getting. That goes for the turbo 350 and 400. If one of these are what you have then you might want to think about an external overdrive unit which mounts at the rear of the trans. That will give you an overdrive gear and at the same time give you mileage in the 15"s. The cost should be around $1,200.00 plus installation.
If your V8 is in good shape. Go for a 700r-4. I have one in my '89. I have a '79 with a th350. It is a gas guzzler. The 203 case dosn't help either. <br>How about your rears? Do you tow? If not what about higher gears. If your truck is 2wd that might be the cheapest way to go.<br>
thanks for the replies,btw my truck is a 77<br>with a 350 trans & 203 transfer case.I've<br>already converted the 203 to part-time and<br>installed locking hubs.I have 3.07 gears<br>front & rear,do little towing and mostly<br>drive to work M-F,do some hunting on weekends, so I use 4wheel drive a lot.My 350<br>is stock with the exception of a dual exhaust<br>and MSD ignition wires and has 130,000 original miles.<br>thanks guys, jay
Jay,stick with 350,you wont get any better with 6 banger.It will work its heart out moving a 4x4 3/4 ton.The money you didnt spend could buy a 700r4 and the Jacobs ign is awesome,it will run so much smoother with that system.<p>----------<br>John D<br>