thats what I would do Adam if'n it were me .  spary the joints with PB Blaster first,  let it sit  awhile,  then they should ( with a little wiggling ) come apart.  If all else fales,  take it to a pro.

the part from Corvette centrel looks to be a direct replacement to me .   the one from 'auto-bone ' looks like it wood work also.  Hard to tell w/o seeing side profile

The red arrow is a hanger. The rear Y-pipe is one piece, and may or may not be welded to the mufflers. If yours is clamped to the mufflers, it's gonna be real tough to get the pipe and the muffler separated. If it's welded, it's gonna be even tougher.
You may wind up cutting the pipe just ahead of the mufflers, replace the Y-pipe yourself, then take it to a muffler shop and have them re-attach the pipes to the mufflers.
Be sure to soak those bolts on the cat/y-pipe connections for several days before attempting to remove them....they look like they ain't gonna wanna let go very easily...you may make up some NEW werds while taking those off!

Is the exhaust system the same for 79 and 80?? or is there a difference?

Forget using PB Blaster to soak them down. Use an angle grinder and grind off the heads and punch out the bolts. You could use a sawzall but the angle grinder is much cleaner.

Joel has it down about the mufflers. If you can cut them off ahead of the bracket or weld a muffler shop can do a nice job for you to reinstall them. Providing they are in good enough shape to do this with. Keep in mind if they weld them back it may not be long before you purchase new mufflers though. Once they weld this older metal it will be weaker on each side of the weld and the lifespan will be less.Tuxblacray2008-10-06 19:03:57

[QUOTE=Tuxmeister]Use an angle grinder and grind off the heads and punch out the bolts.[/QUOTE]

Might be a wee bit hard tuh git at them two bolts on the top there...I was gonna suggest that too, but...

I'm trying to give you guys a big HINT here but all I hear is crickets....

There is room for the grinder with a new wheel in it. Likewise the Sawzall will work easily too...

Remeber there is nothing here to be saved soif you need more room to work you could cut the pipe off enough to allow additional working room.

Course a torch is mighty handy and quick if need to be... (my tool of choice here)

Oh and let's not forget that trusty ol standby... Mr. Hacksaw......   

Or then again you could check with indy99 an' see what he has layin' around from his frame off resto.

crickets.... crickets........"freebie" cough cough  crickets......