Mini Dune Buggy I Am Considering Buying Or Building A Dune Buggy- What Engines Are Feasible?

I am considering buying or building a dune buggy- what engines are feasible? - mini dune buggy

It will focus primarily on the street, but with frequent explosions on my local beach, but the trend is towards the street.

I once have the engine fuel economy and offers traditional buggy sound / feel, and I think it would be a bonus if she was stupid beginner friendly mechanic to work!

People have suggested a mini-motor, or a beetle or an old Ford ... Your opinion?