Making a pickup based on a car with a rear engine is not so good idea, but if you are not afraid of difficulties, then you can get a decent result. As far as I know, the first tiny Fiat 500 pickup was made by the Italian body shop Ghia. It was back in 1962.
The engine was still located in the rear, but the powerplant was changed. Instead of a standard four-cylinder in-line engine, a two-cylinder opposer with a volume of 500 cc and a power of 17.5 hp was used.
Despite the modest engine power, the declared maximum speed was impressive 95 km/h. It got a four-speed gearbox and rear-wheel drive. The transmission, like the suspension, remained unchanged.
This pickup, as far as I know, was made in a single copy. His further fate is not known, but the idea, as they say, went to the masses.
About a dozen Fiat 500s were converted to pickups at different times and by different people. Ghia was no longer involved in these projects. Apparently, the technical part of the master was not touched, so the cars have a very modest space in the back, very little space for the payload.
Although, what am I talking about, such projects are created by the call of the soul, for beauty, and not to bring watermelons to a fair. And someone even tried to make a truck.