I know a guy here in Phoenix who can do the Hurst sawzall transplant in about 4 hours. True, if you've never done it be prepared to screw it up... so best to take it to a professional. But I gotta believe 4 hours work wouldn't come to $1200. That said... I'd still probably go with the Fisher roof transplant too. Better setup all around.
Also, keep in mind that if you do find a T-top 76 it will be a 50th Anniversary car (unless you find one that somebody already added aftermarket T-tops to, or did a roof swap to) so it will be more expensive to buy up front... and honestly, worth more if restored correctly. Regular T/As in 76 did not get T-tops from the factory... only the 50th cars... and then only 643 of them actually got them (even though they were originally all intended to get them).