The 46 heads are about the same, although the source I'm looking at suggests that they might be screw-in studs. They still have the small intake and exhaust valves.
One thing you need to keep in mind is that the HP rating system used between 1970 and 1971. Prior to 1971 the system used was highly subject to manipulation which generally overstated the true output of the engine. It was supposedly based on "gross" HP, in which they didn't count the power taken by the water pump and alternator. Starting in 1971 the system was based on the SAE definition of "net" HP, which was what the engine would actually make when it was installed in the vehicle. There wasn't as much difference between that 265 HP 1970 engine and your 1977 180 HP engine as what you might think.
The biggest gains for the smallest $ are found in the carb jetting and the ignition timing. Stock, those were set for minimal emissions rather than maximum HP and torque. Next up on the improvement scale is the exhaust system. The stock systems were terrible and strangled the engine's output. A true dual setup and a switch from the stock "log" manifolds to either a set of good tube headers or a cast iron performance manifold like the RARE pieces (RAIII replicas) does wonders for the performance -- provided, of course, that you're not living somewhere that emission certifications are needed to be able to drive your car on public roads.
Those changes alone -- even without head or cam swapping -- can really wake up an engine.
