Help with 1st gen tire size

I need LT Tires for my '04 tacoma. I have 3.4L ext cab 5 spd.

Old tires were Advanta Spector or something. They lasted me about 30,000 miles, not bad for a cheap all terrain tire. They were LT265/75R16. This size is slightly bigger than stock tires. about an inch diameter.

I did a bunch of research and found 2 other sizes that will fit. both of these are the same size as the stock passenger tires.

LT215/85R16
LT245/75R16

I drive a lot and gas mileage is a big concern. I'm not sure if a smaller narrow tire will be better or a larger tire with a bigger circumfrence. Most of my driving is highway. I'm sure that switching from an all terrain to a highway tire is going to help with fuel economy already.

Has anyone tried any of these sizes on there 1st gen?

Anyone with insight as to whether a lower vehicle (only 1/2") with a narrower tire is better. I'm not sure if the rpm difference cruising at 60mph is going to offset the lesser rolling resistance.

Thank you for your help in advance. I have a few weeks left on these tires and I will be on vacation for another 2 so I could possibly push these tires for another 2 months. Although the first flat I get I'm putting new ones on. So the sooner I can figure this out the better.