what is the proper rpm for my f150 3.55's stock tires and what would be the best gear for around town driving with 35's.  

4.10-4.56 for a 3spd auto ad 4spd manual....

4.88-5.13 4spd auto OD...  

4.56 minimum with 3 speed and 4.88 or 5.13 with OD tranny if you want it to run and get out of its own way in OD.  

hmmm.. this again...4.10's turn over 2500 rpm @65 mph so...that makes the 4.56 a little over 2800rpm which is ridiculous for a daily driver...this is a ford not a sbc.

the 5.13 with the OD is around 2300 @65  

2800 RPM is not many RPM for a SB Ford at 65 MPH PLUS, those 35's have a lot more drag at that speed and need more power to overcome it. At a higher RPM there is more power available to work with (HP is basically torque x RPM) This is not a diesel and RPM's do not hurt anything and I doubt he would save any gas either because though is it turning more RPM's with a 4.56. less torque from engine is needed and engine is operating closer to torque peak and at a more efficient speed under load. I drove a 72 GMC with 4.10's and 31 to 32 inch tires ten years and over 150K miles and cruised on highway with engine turning 3200 to 3400 a lot and no worse the wear either. MPG was in 14 MPG range at 70 or so too and it ran great and would easily bury speedo too. THere is a false mindset out there with many that less RPM is better but this is the last thing you need with a lifted truck. If you are serious about MPG, you do not install 35's and a lift. BTW, I have long considered that 4.10 with 31's and the standard benchmark for a 4x4 truck with SB type engines, not 3.73 or 3.55's and a 4.56 put is closer to that benchmark. I buy and drive a truck so it is a truck and pulls well, not one that is ham stringed with tall gears for tire size and limited potential.  

that is a big spread in sizes
right now I get good hwy milage with od off and rpm's are a little high but still milage is good.
starting is killin me.
I need just enough to get od back to stock rpm's.  

Well a 4.56 with OD will have a slightly lower RPM that you do now in drive with current axle ratio and 35's. With 4.10's OD will be a slug. It will not be a race car in OD with 4.56's but it should pull it fairly well most of the time. Performance aside just think of the reduction of in tranny strain with 4.56's too which many never seem to consider.  

the OD is a big advantage for off roading cause of the gears you can use and still cruise on the hwy.  

Yes, having OD is a great addition to a 4x4 as you can PROPERLY gear it for power and performance and still cruise nicely. I did not realize that he had OD at first, knowing this now he would do well to consider a 4.88 too as the cruise RPM would be about same in OD as it is now in drive and it would be a real stump puller in first gear and second would not do badly either and OD would pull nicely as well.  

I didn't know either till the last post....