The Panoz LMP-1 has quite a long traceable history for a contemporary and successful prototype.  How this prototype, with its roots based in a GT-1 chassis (see below) and having an unconventional front-engine location, was forged into a race winner is a surprising, yet impressive, feat. 
The front engine layout of the Panoz LMP means a higher percentage of the overall weight is at the forward end of the car.  This has the effect of allowing for more front downforce to be placed on the front axle and therefore larger front tires.  The front engine position pushes the driver back to nearly inline with the rear axle centerline.  The beneficial result is that the driver is better positioned in the chassis from a car feedback standpoint.  With all things being equal to a mid-engined LMP, the front-engined Panoz came with positive design benefits not available to mid-engined cars.  But ultimately everything comes down to a car's record, and that can't be ignored: three wins in '99 as well as the Manufacturer's Championship, one win in '00, two wins in '01, and two wins in '02.