I would suggest that you find out the ACTUAL CAUSE of the problem first. Fitting a radiator from even a Mack truck won't overcome a stuck thermostat or faulty water pump.

It also depends on what engine you are running. If it's a stock or mild 1200, then an original 1200 radiator in good serviceable condition is all you will ever need. Even a mild A15 won't need any more unless you drive it in a manner that provides poor economy.

So check the thermostat, the fan belt, the water pump if necessary, & pull the radiator for a good external inspection & a water flow test.

To test. remove bottom hose, place palm of hand over bottom fitting, fill radiator with water, then remove hand.
There should be a good strong 'rush' of water that empties the radiator in about 2 seconds. If not, then you have 2 options.
Repair or replace.

As I have said before, for most A series engine applications, a 'heavy duty' replacement core will be more than enough & it saves all the hassle of a foreign radiator instalation. Particularly if the new, but second hand radiator is also blocked up.

My new core kept my stock 1200 auto cool on even the hottest days of last summer at highway speeds.
[Actually, it runs just a smidgin cooler at highway speeds than it does at town speeds. Strange but true]

you beter check the termostat and de water pump........

I have had the radiator clean and flowed test and etc and it's all un- block now. Also got a new thermostat which is at a lil higher in temp then orginal. but the gauge still goes straight to boiling even when i just start the car. So im looking at buying a new gauge for the car and i will check the water pump aswell.
Thanks on all advice on better radiator, and i will look around for what i can get.

try a new temp sender before the gauge. Cheaper and easier by far.

The sender unit is easy to test, just disconnect the wire. It just pulls off. If the temperature guage goes down to 'cold' then you know that the guage is OK since it reads both hot & cold.

Replace the brass bulb sender unit in the head with a known second hand one, or new, & your overheating problems should be over.