5x108mm
All model Volvos thru 1989 have a 5 bolt x 4.25" (or 108mm) pattern usually with a positive 20-25mm Hub bore/offset. Even Ferrari wheels fit Volvo!
15.8 Gallons
Yes I believe actually the 1986 to 1992 Volvo 240 4 doors are all interchangeable parts but I'm not sure for 1985 and earlier models.
Battery Group is 47
no,k10042 is an older unit
Above your left Knee when you are driving
Connected to the intake air duct.
5.25 inch
Try the pegasus replicas... they look nice on the Volvo 240 IPDPEG177520 Pegasus Replica - Hyper Black Finish Fitment/Application: 17x7.5 inch wheel 5x108 bolt pattern with 20mm offset Direct bolt on, no spacers required http://www.ipdusa.com/version.asp?strPageHistory=category&numSearchStartRecord=0&strParents=69,467&P_ID=4091&CAT_ID=467&V_ID=10133
Via inflation, if my calculations are right, it would be the equivalent of $36,xxx today.
It's in the trunk. Just remove the carpet and then you see the coverplate.