I'm having trouble finding a bolt in 5 speed or auto in my neck of the woods for my 72' 620. But there are ample gm corporate 10 bolts in the boneyards. That rpute I can get one with a posi and unlimited gearing options on the cheap So I'm thinking about narrowing one down and putting it under the truck when I bag it. Which leads me to this question, what gear ratio should I go with that will give me lower highway rpm's without sacrificing all my power.L16 with weber and L20b cam and factory 4 speed ill be running 225/45r17.