If your dash is black you might be in luck.. I have had some luck with black silicone sealer in the past. Use it sparingly and try to work it into the cracks with your finger tip. Wipe any excess off right away and after several days you can take your finger and rub any extra flash off from around the cracks. This will only work if the cracks have not curled on the edges. It just helps seal the dash so the foam under neath dosen't dry out more and get worse.
It is just a patch and is about what they do with those kits they sell on TV that are supposto patch your car seats and jackets and such. I have a PV 444 and I covered the inst panel with 1/8" foam then black vynle including the cover over the speedo. I filled in the ash tray hole at the same time and it came out pretty good.
Dennis
send me an email at dpflynn@tir.com ref, dash and I can send a couple of pictures or go to the volvoadventures web site in NZ and look under "member's cars and then under PV444 V6 and I think there is a dash picture in that set.
Good Luck !