Hi Richard, I had one of the Musgrove modified Plus 8's and really liked the balance of power and upgrades. It was a 1988 car and had the very rare 4.5 litre cross bolted V8 that TVR used for the Tuscan race cars.
It had a twin plenum, which wasn't so clever but revved freely and put out about 250-260bhp. That was a nice combination and whilst it was brisk, it wasn't overly quick compared to say a decent spec Caterham. 250bhp is not that powerful, so I wouldn't worry about it feeling overpowered, just make sure you have decent suspension and brakes.
I still ponder about getting another Plus 8 and doing what you want as like you, I think you'd end up with a useable car that would be entertaining to drive and I still love the looks and ease of maintenance of a Plus 8.
However, don't forget that most Morgans are restricted on how fast they can be driven by ancient suspension design. A standard plus 8 will bounce like crazy down most typicall British lanes, so put asside some budget to get both ends of the car modified to improve things. My understanding is that big gains can be had with fewer leafs in the rear spings and the Suplex or similar set up at the front.
Feel free to drop me a line to discuss further as I'm still quite keen to do a similar project.
Cheers
Mike
