Morgan Type Trikes
To really mess your minds up, there is another category of trike.  The Morgan type were usually classed as the "originals", they had a style all of their own with two wheels in front and one at the rear.  They were produced with a variety of large capacity V-twins and later, with Austin Seven engines.

There are modern replicas with Japanese motors(Honda CX500 & 650, plus 1100 V4's) and Citroen 2cv`s, also Austin Mini and large engined motorcycle frames welded to a sub-frame.

The subject is too big for this humble site, so I have  just added a few photo`s to whet your appetitie.
Morgan V-twin
Dave Norton's Shrike. Honda 650 four.
Blackjack Avion, with 602cc 2cv motor
Grinnal Scorpion - 1200BMW
Stimpson Scorcher. 1275 GT Mini engine.
Steering wheel. No helmet. Absolutely mad.
Left & above.    The Bugwing.
                    Rex. W. Rosenberg
Moto Guzzi Twin.