That's what I mean by other changes.... You have very limited ratio options with the original axle, but since you made no mention of changing the ratio or related issues it wasn't part of the response.
While you can certainly make changes one system at a time, you'll find it easier to make complimentary changes if you start with a comprehensive statement of intended use.
The cruiser statement you've already made doesn't say to me that the gears need to change. But if you intend to run highway speeds all day you may want something different.
The first step in building a truck is to think clearly about how you will use it.
