55.2-59 another gear ratio question with a bbc

[Spank-a-lank]

I have a 58 shortbed half ton that I am looking at outtin a 402 bbc in. I have had problems finding a manual transmission with overdrive that will work with stock(or close) shifter position and am curious if anyone has used the sm420 with a higher gear ratio in the rear diff.(3.00 or 3.08 depending on axle type) wanting to be able to cruise highway speed ok but also know that the sm420 is a wide ratio transmission. just wanted to hear anyones experiences that has done this or close to it. please do not recommend an automatic as I do not want that. thanks in advance. any real advice/experience welcome.