Excellent choice.
That's the Spectre BGW panel kit. <<
Spectre BGW Ltd. - Rod Conversions Wagons and Vans>> They also have the Venus Van (originally Domus or something) which is boxier.
The panel van kit closely fits the ideal aerodynamic profile aft of the Beetle's B-pillar. At least according to my investigations:
Look at me, going off-topic. That's a subject for
another thread.