I would start with a 262C body and its far more laid back windshield and lower roof line, add newer B230/LH3.1 engine, M47 gear box, 3.31 rear end, flat hood with covered grill, skinny bumpers (weight), belly pan, newer driver's side mirror, no passenger side mirrod and voila. You would even have a good excuse to cover up the the rear wheel arches. That combo will be worth 35mph on the highway easy.
http://www.isaab.net/upload/VOLVO%20262C%201979..jpg
But thats just me
Sorry for taking it OT.