From 1972 to 1979 the VW micro bus uses a type IV "Pancake" version of the air cooled flat four motor. Pre 1972 VW buses use the upright air cooled motor identical to the versions used in the VW Beetle's of the era. VW then experimented with a water cooled version of the flat four engine(Wasserboxer), this lasted a few short years and VW moved all vehicles to their water cooled inline and similar standard engines.
Open the hinged dash panel to the left of the steering wheel. The flasher is the black box behind the mass of wires, attached to the cowl panel with one screw.
Although, they are both Type 1 cars. The floor pan for the Thing is different than for a Beetle. One might fit on the other, but it won't necessarily be a perfect fit.
The VW "Deluxe Beetle" sold in the US (I don't know what a "standard" one looked like) held 10.6 gallons, or 40 liters. The "Super Beetle" held 42 liters.