The stock rad tanks can be fitted with 3 cores (I did this)... I don't think there's room for the 4th (you'd need different tanks).
It's tough to diagnose when you don't know the history.
If you've still got the stock water pump, it probably about shot. I HIGHLY recommend the
www.stewartcomponents.com pump.
If it's got the stock catalytic converters, they could be getting pretty clogged. This would really heat it up.
If you get a 93+ starter (mini/perm-magnet), you'll be able to start it when it's hot... but you really gotta fix the problem.
Also, check the timing... should be around 10-12 degrees BTDC.