roadster vs locost?

[skov]

The wiring is probably more complicated if you take the MX5 route.
The rest isn't any harder, and in some ways it's easier as you don't need to make new rear uprights, or add those mushroom things to the front ones.

Not sure it's any more expensive either. The donor might cost you slightly more than a Sierra but MX5 parts are still in demand and you can cover the cost of the donor (and even make a small profit) selling the bits you don't use.