Heads and cam swap

If you get a good running 360 mag with under a 150k for miles, I wouldn't even do bearings/rings. These will push 300,000 miles without batting an eye.
They have around 245 hp (NET) hp from the factory, which would be about 300 gross. You'd get this with just a 4bbl.

• Heads are a nice upgrade
• Your 4bbl will add some top end power, as the keg intakes choke out the rpm's
• In a 4wd, you may only want to upgrade the heads. You may like the cam as it has good low end torque.
• You are correct with the manifolds, some have bigger outlets. A good dual exhaust ran off of those will aid in power too.
• Good Luck :)