Unless you are going racing, I'd only have the flywheel lightened. The internals are better off just balanced and left understressed.
Unless of course, you like the Lotus method of having an engine last just "one race." Colin Chapman was quite the advocate of "adding lightness" and a lot of his cars had it added to the hilt.

Good find on e-bay. Hope it works out properly. Last one I got (B20) I had to give a bit of a "freshening" to and probably should have fully rebuilt it.

Pistons should be OK unless severe scuffing took place or the ring lands are worn (or the pin keepers sprung out or the wrist pin was bent or...). I've polished off some slightly damaged skirts before (although most builders tell me not to) with good success... not at 7k rpm, however!

Heck, tear it open and let the fun begin... It's not going anywhere!

Mike!