If the temp goes much above your thermostat's rating, you need better cooling system. Maybe not a larger radiator, but think about airflow (radiator blocked by intercoolers, sheet metal, etc?) and fan. A lot of electric fan setups are poor, the stock engine driven fan is fine for a non-boosted engine. Or maybe a better radiator. The stock one cools a stock or moderately built engine just fine unless it is partially corroded inside or out.

well i have a near new radiator (replaced about 2 months ago with a brand spanker) and i installed a thermo the other day which helped, by about 2 degrees :( ... ah well im putting the weber and extractors on on saturday so i've got better things to worry about.

anyone do a larger aluminium rad for these, ive seen a couple on cars that have been 'maddated' lol coz i'll be putting twin side draghts on soon and doing a little bit of work to the head

I like to see the temp stay below 100 degC in the race car, but I have pushed it to 105-110 on really hot days during a race and stuck behind another car...... In a street car, a good fan with adequate radiator should be able to keep things cool.

my a sreies never went above 80c with a 175 genuine thermostat and gemini radiator and a good pump with good blades cause they corrode off. no matter how hot outside no matter how hard i pushed it when racing.
oh if its a hi-po a series fit an oil cooler they need them

Yes have to confirm that a oil cooler is a good idea on tuned engines as mine went over 160'C just driving down the street and back again.
Cooling fans are no good unless your driving Miss Daisy. Good coolant is a must.