Here's what I'd do mate if the engine in the sierra is ok. Or if you haven't brought the sierra yet...... buy one with a cvh engine.
Build the roadster with the cvh in SVA it then change the engine after. well thats what I'm doing. Hopefully with bike carbs too
I dont know anything bout swapping the zetec into the sierra but I think it would have to be done fully up and running. Do they need to inspect it aswell?