Swap Ring and Pinion or New Rear End?

[Shorthair_Hunter]

When I traded my 71 GMC C20 for an 85 Chevy K20 last year, the guy told me that the PO had swapped the rear end and the gears no longer matched up with the front differential. Other than that, the truck was great and it was an awesome deal, so I made the trade.

The spid in the glovebox says 4.10 gears so I assume that is what is in the front. I'm also guessing that the rear is something like a 3.73. When I was driving in 4wd recently, my dad was following me and said he could see my rear wheels kick up on occasion which tells me they are moving a bit faster than the front. It also felt lurchy around corners, straightaway not so much. At most I went 20 mph.

So - would it be best to get a new 4.10 ring and pinion to put in or go junking and find a complete axle that already has the right gears? I have heard the pros and cons from a few people I know but wanted to hear from the wizards on here before I made my decision. My current axle is a GM Corporate 14 bolt, 8 lug.