Odd I thought it would be a BSc not a BA?
Still the Morgan 3 wheeler had good power to weight and for this reason remained competitive into the sixties as a sidecar racer, the greenwood mini took this a stage further by utilising the front wheel drive front end of a mini with a single back wheel, annoyed the biker types no end!
If you are looking to simply update the 1935 barrelback then a front end V twin from a Motoguzzi would do the job, a V4 from a Honda Trans European a Ducati engine is assymetrical so would look wrong (but sound nice)
Go to emog group, there is a gut there called John H Shealley and he is a very well known now retired professional photographer and racer of Morgans, Bugattis and such, he really knows the quirks of these cars, I have never driven a trike so cannot help you more.
Good luck
Chris444