Always liked the Marlin, a very pretty little car, Alfaresque, if there is such a word and yours looks great in white. They did a four seater too I think, also rather nice. If I were rebuilding one I guess a Toyota 2000 twin cam and 5-speed would be a nice way to go. You could make it look very much like a period Alfa. Mazda MX5 would make a great donor also, and there are quite a few rusty ones around now.