and there is more...
The surface area of the swap, might be close (54 V 69) but the air flow and pressure are completely different.
somewhere online is a schematic of the mgf airflow.. i will look for it unless someone has it to show... the most still air is where the air intake pipe sits.. down near the rear bumper..
even a slowly moving f will push more air through the rad at the front than the side air vents can...
The other problem of putting the rad at the rear.. is that coolant has weight.. and if you remove that from the front. the front gets lighter.. the car is balanced taking the weight of the rad, the coolant, and the pipes that connect to it... weigh them filled with water, and see how much weight you will take off the front of the car.. and how much therefore you will move to the rear..
And thats before you put things in the boot..
so the car will become unbalanced, you will skate and aquaplane with less weight on the front wheels. thats why even the weight of the spare wheel is taken into consideration..
a better idea is to leave the rad where it is but change how the cooling system works.. ie do away with the thermostat, and consider using temperature sensing flow valves... that are normally open.. ie fail safe.. but are closed dependent on temperature sensing at various points around the engine and engine bay and rad.. ive considered that.. i think it might need up to five valves.. in the hot line pipe to the rad. under the passenger floor.. ie the incoming pipe to the rad has a junction that splits into smaller pipes each with a valve in... that are closed dependent on temperature measurement sensors, placed elsewhere.. and then join again with the pipe to the rad.. probably where the union is now..
so... when its very cold.. they will all close when the ignition turns on... and as the engine warms up, they will open in turn.. until they are all open ( all turned off )
such a design means one can have flow through the rad at all times since even if one or more valves fail or the temperature sensors fail... the valves fail open.. its fail safe.. turned off, they are open.
Of course one needs to consider what happens if a temperature sensor fails reading low temp and keeps a valve shut.. but five all at once is unlikely.. and if one stops and turns off the ignition, the valves are open... one could even have a manual overide, and turn them all off. ( open )
it would be less effort to do that...... try taking out the thermostat for example , and one will see that with constant flow through the rad, the engine wont reach operating temperature... the coolant is being cooled to much..
with some constant flow through the rad, it wont clog up with sediment.. that a plus in itself..
here is page three, of the topic i ventured here..
Using temperature based flow control of coolant
you can read the whole thing. i explored rev sensing and temperature control - two things operating at the same time..
but my circumstances changed .. i still think is a good idea, but i havent built it yet...