Hi I have a 72 zed (very much a project) and an 84 Nissan 720 pickup 2.4 L engine. Neither are my daily driver. The alternator in the truck went a few years ago, and I purchased a new one. When I was putting it in, I being stupid at the time did not disconnect the battery and got a huge spark touching the alternator to a live wire. I figured I may have fried it. After I put the alternator in, my battery warning light came on dimly and constant. So out of frustration, I took the alternator out of the zcar and it fit. Although the light came on dim as well. I eventually stuck the new alternator into the 240z and it seems to be ok. I am actually quite surprised by this.

I am now doing some work to the truck to sell it. Difficult to sell with a bad alternator and I don't want to put $180 bucks into it to sell it for $1200. Especially now that I don't think the new alternator was fried but is the wrong amp. I suspect it is 50 not 60. So... I went to the local boneyard to find an alternator. I have since pulled two one from an 84 stanza - got it home and it wasn't even a close fit.

Had a closer look the next time I went, and bought another one and it is close

but the housing for the top bold is about 1/2 " back so it doesnt fit either.

I really want to find a $20 alternator but Nissan 720s and 240z's are hard to find in junkyards now. Question, what other cars would likely have an alternator that fits the z or 720? Would a 280zx 60amp work? what else?

The problem with the first part of your question is that, unless someone did the conversion, your 240 alternator is externally regulated and will not work properly in the 720. And since the 720 alternator is internally regulated, it won't work in the Z without modification to the wiring. I would quit experimenting before you have two bad alternators and possible other electrical problems in both vehicles. Put the 240Z alternator back in the 240Z. A 720 pickup uses the same alternator as a 1978-1979 200SX, 1978 F10, 1979-1982 210, 1983 Pulsar, 1979-1982 310, 1983-1986 Pulsar NX, 1982-1984 Sentra, or 1978-1981 510.