If you want to know the records have a look
here.
But most of those will be with non-standard fuel tanks added.
Not only does Dick Rutan have the overall record, but he's there in Class C1B (piston) with a Long-Eze flight from Alaska to the West Indies and C1B (Rocket powered) with a flight of 16km.
Ferry pilots regularly take fuel for 2,000 NM plus (or nearly in the case of the C310 pilot in Hawaii last week!).
Maybe you want to be more specific, like unmodified, certified, standard category. You might then get more specific answers.
Last weekend I was managing 152 KTAS at 10,000' and 6.2 USG/hour in my RV by running LOP at 58% power. That would give me over 1000nm on standard (42USG) fuel, so doubling the fuel capacity could give me maybe 2000nm and still under MTOW solo. Go over to Santa Paula and talk to Klaus Xavier and see what he's achieved in his Eze.