i see that you are relying on the body to transfer the entire grounding current to the starter, it would be wise to use a cable from the battery coming to the transmission casing. Your cars body may start to rust out from electrolysis if you dont fix it.
If I were to put a big iron block engine into that car I would have a custom made radiator that can tuck into the radiator support and span the whole front, the cap would be eliminated from the radiator - and you can use either a remote cap setup or remote pressure bottle setup like MB, VW etc.
