Well, you're weird, but we still love you.
For a swap, there are a couple of factors that make the 260 an excellent choice.
First off, do you know what makes an onion different from a 260Z? People cry when you cut up an onion. Being the least desireable Z (due mostly to the square-top carbs than anything else, I think) nobody cares when you cut one up. But they're still lighter than the 280, so you get a bit of performance increase there. Not much, but a little.
Secondly, the electrical systems were a bit more sophisticated than the 240. A shunted ammeter keeps dashboard fires from happening, and the fuseboxes don't overheat AS readily. Still not perfect, but better than they were. THey have a bit less wiring to rip out than a 280.
If I were to do it all over again, I might choose a 280 instead of a 260, though. Stronger bodies and better insulation make for a more liveable car for many folks. I'd give up a tiny bit of performance for a tiny bit more comfort.