iv'e got a '73 240z with the square top su's, they have been rebuilt and syncronized the car runs pretty good. the car does not like the heat at all, it wants to vapor lock but i've gotten that mostly under controll. the problem i have now is that i can't get it to start when it's cold. once i get it started and warmed up it runs fine but the cold start is very difficult. does anyone have any ideas?
Your vapor lock problems are under control because, its WINTER.
I have a 73 that had flat tops, the car is rust free because it was very hard to start in the winter, so it never got driven in the cold or snow. After 3 years of that, the carbs got swapped out with the round tops. No problems since.
The hot and cold problems are the nature of the beast with the flat tops.