Bob
At the risk of putting a dampener on your plans , I would advise trying to see if you can find someone else who has done this and trying their car for yourself.
Wider tyres may give more ultimate grip in the dry , but they are not necessarily a good thing , especially on a Morgan.
The +4 is nimble and chuckable, the wider tyres will possibly hang on for longer BUT when they go you will be travelling at higher speed and catching them will be that bit more tricky. I think it was Tim (Hamwich) who said you want to choose tyres which you can break traction at low speeds to have fun, and will be controllable when drifting at higher speeds. Wider tyres won't help in either respect.
The 205/60 x 15 is a standard size for the alloy wheeled +8 , and I think that it over-tyred, a +4 needs a narrower contact patch to maintain its handling.
