I've always wanted to do this, but never got to the point of attempting it.
After doing the current car, I'm pretty sure it wouldn't work out much different if not cheaper than trying to stick to an original arbarth spec!
I'd be tempted to stick a Bmw twin in though, or Ducati for the twin noise and torque ?
I'm sure its a cheap way to make it fast- but it misses the point in my opinion.
I had a big Healey and making its lorry based engine racy was much more fun than sticking an American V8 in it...
They lose something vitally important when a different power unit is used. .....