Need some help I have a 494 bbc that's going into
The 86 I roc can I build the rearend to handle
The torqure or find a 9" ?
Thanks tommy

 

The other options would be a 12-bolt or a Strange (Dana) 60. They are both lighter and mechanically more efficient than the 9-inch. The issue with a 3rd or 4th Gen is the need for the rear to have the torque arm mount, so that means you either have to have a high level of fabricating skill, or buy a direct bolt-in from Strange or Moser. You're looking at $2,500 - $3,000 for one of those.

There is no way the stock GM 7.5"/7.625" 10-bolt will live behind an engine like that. I don't know if GM used the Borg-Warner Australian 9-bolt in the 86 IROC, but I doubt it. They are a bit stronger than the 10-bolt, but not much.

I have a Strange 12-bolt behind an engine making 800 HP/800 lb-ft at the flywheel, and that's probably the upper limit for the 12-bolt.