Anything less than $100 would be fine bargain in my opinion, assuming you reaaalllly care about going 1,000 miles between filling the tank. I'd be interested in knowing who built the 40 gal. fuel tank and whether it's some sort of Stuttgart option we have never heard about.

Also, take in perspective the fact that your 300CD trunk will lose storage space..... possibly important if you carry two bags of clubs 24/7 during golf season.