Rear end gear ratio - making my head hurt

[bikeguy]

Ok, need a little help with this decision. I've been researching for the past couple of days and can't make my mind up on which gear ratio I should change to.

I restored my 1970 Chevy 4x4 truck a few years ago. The engine is a 350 4 bolt main, when I rebuilt it I ended up boring .30 over, and installing a mild cam. Originally equipped with an SM465 4 speed and NP 205 transfer case, converted it to a TH350 with NP 205. Front and rear ends are non-posi (open) and 3.08 ratio. Currently running 35/12.5/15 wheel / tires.

Driveability is ok, a bit sluggish off the line, but does ok when cruising at 50. Today my son and I were driving and verified with his GPS that at ~55 MPH engine was turning at 1850 RPM's.

From what I've read the optimal RPM range should be a bit higher. I've been thinking that I need to go to at least a 4.11 gear or maybe a 4.56? I like the 35" tires so I will be staying with that size tire. Also this is a city driver, not much time on the freeway, but I do go on longer trips occasionally. I don't tow much with this truck, just like to cruise.

So, the question is, which gear ratio do you guys/gals think I should go with? Also, here's a pic from when I finished the restoration.

Thanks for your help.