Hi Andy,
Thats quite a find at that mileage, delighted that you're also interested in these older Volvos
I've just looked up the Amalthea wheel and it is a 17x7.5" with a 49mm offset. I have a set of Comets fitted to my '97 S70 (so the same basic body/chassis as your V70) and these are also 17x7.5" but with a 43mm offset, so 6mm difference.
The tyres on mine are 225/45x17 and they fit ok, but they do rub at full lock.
A few links for you to browse
https://accessories.volvocars.com/en...CC-425368/2001
https://accessories.volvocars.com/sv.../R.H.D?lang=en
Hope that helps
EDIT - I've just found out that there are two sizes of Comet wheel - 17x7 and 17x7.5 (called Comet 'C') and as I'm not sure what mine are, you should disregard my comments about them fitting ok - Just in case mine are 7 inchers! Sorry about that - I only found out by reading through the accessories catalogue on that website!