The biggest thing is that the valve stems have to all be set at the same height when the valve job is done. Next, you have to assemble the block/head and measure to get the correct pushrod length, especially if the head/block have been milled.
Besides the proper rockers/shaft/cam/lifters/pushrods you will need pushrods and the late model oil pump.
Finally, if you have the early design head that takes the 3/8" bolt in the rear rocker shaft hole, it may not flow enough oil to keep the lifters pumped up. The solid lifter heads changed to the stepped bolt around '76, and the hydraulic head came out in '81.
Frank is right, cam selection sucks.