a little more confirmation...
*There are some important differences in the CV jointed half shafts for the 280ZX and the 300ZX. I will briefly list them so that replacement parts or salvaged parts might be found easier. From the data found in a CV joint rebuild guide that I was able to look through, I found that all the '82-'83 280ZX Turbo's and some of the 2+2's use the same exact half shaft. These half shafts use a "tripode" design in the CV joints, meaning they have a 3 pronged (120 degree), needle bearing equipped joint. The axles themselves are 14-11/16" long, both left and right sides, and have 27 tooth splines at both ends. All other 280ZX's use the U-joint type of half shafts. The differential axle stub assembled as part of the shaft has 25 teeth in the splines that will fit into the R200 "Z" differential.
The '84-'89 non-turbo 300ZX half shafts are almost the same as the 280ZX shafts, except that the axle lengths are 15-3/4" long for the right side, and 15-3/8" long for the left side, but the ends of the axles themselves have the same 27 tooth splines. If worst came to worst, I would check your specific car's dimension to see if there is enough lateral movement in the CV joints to be able to use these longer axles, without any binding, provided you changed the inboard differential axle stub part. The differential axle stub is assembled as part of the inner joint, and has a different set of splines than the 280ZX, so this end won't interchange either. But, the good news is that the tripod assembly itself, that fits on the ends of the axle splines, are the same between the 280ZX and the 300ZX shafts. On the turbo versions of the 300ZX, Nissan went to a more traditional ball-and-cage version of the CV joints used on these half shafts, with no interchangability of their parts.