It doesn't go by VIN, but date of manufacturing.

Look at the white sticker in the inside of the drivers door. Mine has built 7/98.
If yours have a date of 3/98 and later, I'll bet you have a late model. Remember that the '98 model started selling in the fall of '97 with built dates of 6/97.

The definite way to see if yours is a late '98, is to take the cover of the t-belt housing. This would accomplish two things: 1) you get to take a look at the t-belt. If you see cracks or if looks worn, then change it now. And 2) see if you have the hydraulic or mechanical tensioner, volvospeed.com bay 13 has a picture of what the hydraulic tensioner looks like.

Remember the most important thing is YOUR CONFORT LEVEL. I feel fine taking mine to 95k miles, but you might want to change it at 70k miles or even at your current mileage.

Cheers.
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'88 240, '92 745, '98 v70 John, Tampa Bay