Well, you would put in different pushrods. The tops of pushrods for those rockers have cups, not balls, and IIRC are of a different length. The original length's ought to work if you have not milled the head or block excessively. But it is always wise to check the pushrod length.
The adjustment is simply a threaded screw on the pushrod end of the rocker with a lock that allows you set the pushrod so that, with the valve closed, it pushes the plunger in the hydraulic lifter down in the range of .040". That is called 'lifter pre-load' adjustment, and you can find lots of threads here discussing that.
The shafts and rockers just bolt in place like your present rockers.
Google for '273 rockers' and you find all sorts of pix.
