Hi Geoff
Welcome to AO. Lovely looking car you've got there!
It sounds like you've got some wires crossed somewhere when you put the new ignition barrel in. I would concentrate on that bit before you start dismantling anything else.
As for the engine, you'ev hit the nail on the head. It's a bit newer and more powerful, but it does affect originality and value. It depends how much of an issue that is to you and how much you paid. To be honest providing you didn't pay a huge premium for a matching numbers car, I would just enjoy it!!

Cheers
Rick