quick question. is the rear brake assembly from a 280zx a direct swap to a 74 260? or is there modifications that are required. thanks

Nope. You'd additionally need a Maxima bracket at least. The rear brakes on a '74 260 are drum, while the 280ZX has disc. If you're looking for conversion to disc, your options are listed here: http://forums.hybridz.org/showthread.php?t=104735
and here:
http://forums.hybridz.org/showthread.php?t=103767

The 280ZX installation on the S30 requires the Maxima bracket listed in those threads. The pros and cons of each of the options are listed there, too. Basically, you have to decide on trade-offs about parking brakes, money, junkyard searching, and time. At least there are a lot of good options from which to choose.

cheers,
Dave