Want to build a good horsepower, good fuel economy engine for a 1978 c20 with stock 350. I don't know much and need help.

[Grit dog]

it runs pretty well and as far as i can tell its in good condition

This begs to be discussed, but no one has posted a comment along those lines.. The following is only my opinion but should be considered...

One word: WEIGHT.. Personally, I would never consider a 3/4 ton when designing/building a performance vehicle. They're just too heavy. A 1/2 pickup is considerably lighter and will outperform (acceleration, mpg, and comfort) a similarly equipped, and geared, 3/4 ton, simply because it is lighter in weight.. And the routine maintenance items -- brakes, tires, suspension and steering components are more expensive to replace on a 3/4 ton.

Quinn, this is totally your decision, but is it possible for you to retain the 3/4 ton for daily driving. Maintain it properly for dependability.. Locate and purchase a suitable 1/2 ton short bed and build it to your goals.. Trust me.. If you stick to a single vehicle, there will be times in its construction where it will be disabled while you're working on it.. There will always be situations where the particular project can't be completed on days off or in a weekend. You'll find yourself afoot, looking for a ride until that particular project is completed - and there will be plenty of these situations....

@RustyPile I’ll have to disagree on the weight thing. In your example anyways. The baseline difference between a C10 and C20 long beds is like 400 lbs.
That’s not much. <10%. He’s not bracket racing. He’s a 16yo kid with an old pickup truck and a 16yo budget.
Or at least, weight is about the least significant part of the equation in this young man’s scenario.
The overall condition of the truck is primary.
Gearing second, and everything else from there is $/mpg or $/smile.

 

[Grit dog]

Ok, I have to be the guy to ask. Since he is talking about making some very significant upgrades to his motor to get MPG along with his low-end torque and power, would he be better off throwing in a 4-speed transmission with a good torque converter instead to help with his power vs. MPG balance? I swapped the 6.2L Diesel to a High output 350 and my MPG is terrible but I don't drive a SB for the MPG. I can say driving 70 down the highway at 1800 RPMs is a pretty good feeling though and at cruising speed my MPG is decent. Thoughts?

Depends on his intended use and abilities. ROI on a OD transmission swap is not likely to be realized for quite a while unless the kid is pounding it down the freeway daily. In which case mpg will still basically suck compared to any small/med size fuel injected vehicle. At that point the square becomes a cruiser and a beater car that gets decent mileage is more advantageous.

 

[Grit dog]

@Quinn_Hanifan
Sounds like you got a cool truck on your hands.
One word of advice, it all costs $$. Prioritize what you want to accomplish before diving in. (Which you are so far by asking a lot of questions and learning a bunch).
You can probably sense where my priorities would be, in your shoes, based on the last couple posts. I was working on and hot rodding cars when I was your age and now our sons who are basically your age 17&21 are doing the same. Keep it up!
If your truck is cool lookin, and of course kinda rare if it’s not just a rusted heap back in the salt belt, that is 3/4 of the battle. No one else likely rolling up to high school in a 40-50 year old pickup!
Not to dissuade you from more power AT ALL, but what I’d do based on what you’ve said about your knowledge so far and what you have to work with, is this.
Keep that good running truck together. Spend some time focusing on the “small stuff” that costs little or nothing and makes it better. (Like cleaning up the grunge under the hood you mentioned)
If you want more power on a budget and a realistic plan you can tackle, search and save for an engine that is already built around what you’re wanting (like used,Craigslist). Be smart about buying it, ie judge the seller and don’t buy anything you can’t hear run or doesn’t come with recent rebuild receipts at least. When you have that engine, sell yours (running and driving = more $) and swap in something with more than the colossal 70s 165 hp beast that is under the hood.
Hell, that’s my plan for the new 77. Don’t fix what ain’t broke, find/build/buy the engine I want, then sell the new rebuilt 350 that’s in it while it’s still in the truck and someone can drive it. Yank that motor upon sale and off to the races!

Great experience “building” an engine, but imo at your age and knowledge, far too many areas to mess up or overspend and a greater chance of having a pile of engine parts under your hood that no worky.