New guy here, I'm a lifelong Chevy guy but I'm buying an 85 half ton long box 2wd from a family member for a pretty good price. It was originally a slant 6/auto truck but it has been swapped to a 440/727. I'm sure I'll have a lot of questions, I haven't had a chance to really look it over, but I'll be picking it up next week and getting started on cleaning up a few things. I suspect my first concern beyond the basics will be upgrading the 8.25 axle and give tuning the engine.

 

Welcome to the forum.
Looking forward to seeing a picture of your new ride.

 

I was thinking about this and thought about the 9.25 axle assembly from a Dodge pickup would probably be the best bet for your truck, 3.55 gears and limited slips are common. The other way to go is to change the front to the 5 on 4.5 bolt pattern and look for a 8 3/4 axle from a 60s or early 70s pickup.

 

3.55 with limited shop would be perfect. I've got a lot of little things to worry about before I go out and try to break the stock differential. She's confined to the garage until the salt is off the roads.