Just picked up a decent f150 300 strait six auto trans 2wd ext cab long bed very good condition very clean 150k miles for 1000$ I'm going to be lifting it and putting 35x12.5 under her , I drive about 50% highway and 50% town avg speed bout 50mph what's the best mpg rear end ratio for that ?

 

For a 4.9, 4.10s would be plenty imo. I'm running 33s with 3.55s and I'm happy.

 

If it already has a 3.55 you would probably be ok. Would be a little sluggish on take off but it would help on the highway as far a a gas mileage. But if you have a 3.08 I would agree and go ahead and go for a 4.10 or a 3.73 at the least

 

If it was my truck it would be getting 4.88s or 5.13s. 4.88s would put you right at where a truck with factory 4.10s and stock size tires would be

If your only cruising at 50 mph then you can get away with really deep gears without your cruising RPM climbing to high. You should only be running around 1600 RPM at 50 with 4.88s or 1700 with 5.13s.

 

Thanks for advice I think I'm going to do 4:56

 

Not many trucks have factory 4.10s. I wish I could find a set though.