I need some advice on which swap I should do. To get better MPG for the money. C30

[jarrodblake]

So I am getting close on finishing my c30. Should be in paint next week. So I have a 1970 C30 ramp truck. It has the stock 4 bolt main 350 with 68,000 original miles. I assume the trucks weight is somewhere around 7-8k and I get about 4 MPG.

So in my quest for better gas mileage this is what I have come up with. Please correct me if I am wrong.

Option 1

My first thought was to install a Holley sniper EFI conversion kit and install a HX35 turbo I have. I can probably do the conversion for a little over 2k over time. I would do the EFI first then the turbo later. So $1,400 up front. then another $1,000-1,200 down the road when I turbo it. So a total of $2,400-2,600 However I don't see getting any more than 10-12 MPG out of it. That said I have a Chevy NV4500 getting ready to go in so that could help MPG. But the cost to do so are more than I want to spend for what I would get out of it. So I probably will not go this route


Option 2

Would be a 6.2 Diesel. I can get one for around $800 that is complete and running with low miles. I have access to two one with 82k that has been sitting for years and one with 125k that I know runs. They will bolt to my nv4500 and I can probably do the complete swap and turbo it for $1,400. Minus me selling the stock engine and junk 4 speed trans let's say $500-600. So around around $800-900 total.

It should also get better gas mileage than the 350 EFI. 10-18 MPG


Option 3

I want to do this one the most but I don't know if it would be worth the cost and time. I can get a complete good running 12V cummins with 270,000 for $2,700. But I would have to get a different trans or Find the parts to adapt it to the cummins. It's a 95 NV4500 so it has the same gearing same first gear as the cummins so it would be easy to swap the input shaft. Then I would have to find a bell housing mill it down and redrill the bottom Bolt holes. My only concern is modifying the input shaft retainer. I can't seem to find a thread with pics and that go into detail on how it is done. It would probably cost around $3,700 Minus me selling the stock engine and junk 4 speed trans and the chevy NV4500 let's say $1,000-1,200. If I do the conversion to the trans it would still cost about same as selling and buying a different trans $3,700. So around $3000 total after selling the engine and junk trans..

It would also get the best gas mileage out of the 3 18-30 MPG

Cost and MPG may vary, but that is about what it would be.

So its $900 vs $3000

I know the cummins is the better engine, more durable, more power and better gas mileage to weight of the truck. But the price difference is huge and I don't know if I will use it enough to justify the cost. But at the weight of the truck 7-8k and it will probably go up as I want to add a lot of tools and equipment. I just don't know if the 6.2 will handle the weight of the truck.

Something to think about.

The truck as it sits has a 17 foot bed I plan on bobbing it and making the dovetail removible giving me a 12 foot bed making the truck more manageable and useful. With that said I will still only drive it a few times a month.

Starting next year I plan on buying some property and moving across country. This truck will getting used a lot next year during moving. I will also use it to haul equipment to clear land on the property.

Pic of the truck before restoration.