Wondering if there are any bolt in solutions for an open rear? It is an 8.75 and has an 489 case. I was looking at a locker that allowed turning, but not sure if that is the answer?

Dr.Diff on the board has new sure grip units for sale that are a true retro fit.

Powertrax Lockrite Lockers are supposed to be bolt-in and good units from what I've heard. For as much as you'll spend on one though you might as well drop a little extra coin and just buy a new Power-lock suregrip, or Detroit True-Trac, or a Detroit Locker and pay the hundred bucks to have it set up right unless you can set it up yourself.

You can also use a mini spool but be careful around the corners

They're all bolt in.... If your asking can you replace the spiders with a locking unit and not disturb the carrier? No such animal that I've ever heard of. The powertrax are aggressive, noisy, and not really much cheaper then the new clutch type sure grips Dr. Diff sells. You'll not go wrong dealing with him. His reputation is impeccable here. Hope he chimes in

Yes, I just bought a quantity of repro clutch type power-lock differentials. They don't cost much more than a lock-rite.