What is everyone running in your K20s?

[RaptorSentry]

Currently running a 350 with the TH350 transmission, wondering what everyone is running.

I would like to improve fuel economy and ease of use by either modifying the original engine/transmission or replacing the engine/transmission. Not looking to tow, but still be able to haul a load of gravel in the bed with ease. Here are a couple of options I am looking at and would like some feedback:

1. Keep the 350 and install fuel injection kit, such as the Edelbrock Pro-Flo 4 EFI Kit. Then add a gear vendor Under/Overdrive.

2. Do the same as #1 with the engine and replace the transmission with a 200-4R, 700R4/4L60, 4L60/65-E, 4L80/85-E, 6L80/90-E, or the 8L90.

3. Go with a 6.2L Banks Turbo Diesel with any of the above transmissions.

4. Go with the 6.5L Turbo Diesel with any of the above transmissions.

5. Finally, this is Chevy Performance recommendations, is to go with the LS3 with 4L70E.

I am thinking the 6.2L Banks Turbo Diesel with the 700R4, would give me the best fuel economy (Annual Fuel cost) and still have enough power to haul a bed full of gravel.

Any thoughts?