Your cross referencing says that because of the electronics. The 1998 is very similar to the 1997 and in many ways the 1999 but in 1999 they added some serious revisions to the electronics - electronic throttle, stability control, variable valve timing, I think even the fuel system is different. Unless you're planning on taking wiring harnesses and computers along with your new engine I suspect it will be easiest to transplant a 1998 engine. 1997 as a second choice in my books, but I've never done this job before.

I understand where you're coming from but I still think personally I'd prefer a rebuilt head, all cleaned and polished and newly planed and sealed... and if you end up doing a piston or two I don't know how much that would add to the headache... seems to me you can do a piston from below with the oil pan removed but maybe I'm dreaming...

Also I've heard a few times that the pistons are normally damaged much.

Nonetheless I hope you find an engine nearby that will work for you.

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1998 V70 AWD->FWD Turbo 200k+