The thing with the stamped HP on the cars is that for a while the manufacturers would stamp the se HP on them witch is the engines HP with out anything hooked up to it like ac, power steering or drive train that's why the numbers where so high. The government butted in and told them to put the NET HP on the cars, meaning the engine had to be dynoed with all of its accessories and drive train. So now the numbers are lower and you also have to take in consideration that smog became an issue and performance suffered... Hop it answered your deelema...
it might not have ether of thous but it still has the trans and drive shaft and its a nown fact that a car can loose about 20% of it hp threw the drive train.. and the 280z's are light compared to the newer 280zx and their engines are difrently built in the sence that the olde l28's had dish pistons= to higher compretion and the newer onse hade dished piston= lower compretion (and smog reduction)..... as for the s130 and s131 they are chassis numbers of the car... they use them cuz that same chassis is use all over the place but with a different name and thats like s14 is the 240sx/silvia