There is a "genius" in Indiana who has hacked the Prius software and built a plug in hybrid using the standard hybrid battery pack. Bob, this is your type of guy--if you haven't made contact with him yet--for your adventures. I'm on a dial up--away from home- and I can't search too well to relocate this individual.

2005 AWD Escape Hybrid
Best tank trip MPG 39.02 (scangauge II) for 402 miles on I-70, 10.3 gallons used over mostly flat terrain.

Best tank trip MPG 34.6 for E30 for 271 miles along I-80 in Indiana and Ohio.