One last thing I notice its an auto. They cool through the bottom of the rad, the jackets split, 10 years is the max they will last, if the rad has not been changed in the last 5 years change it. If water gets into the box its toast in about 2 miles. The boxes have an external filter about £40.00 for a proper Mitsy, check the fluid there is a dipstick in the engine bay mine was on the right hand side, the fluid must be a nice red, the box holds about 8 ltrs and there is a drain plug so no dropping of sumps, do not use Dextron III it must be Diaqueen spec, or I think that is what it was called. I used Amsoil in mine fully synthetic, cost about £14.00 a ltr but about the best you can get. If gearbox is jerky and wont shift smoothly and those boxes are very smooth then its either old fluid burnt brown colour or the wrong fluid. I think all the radiators are the same for the 2.5 and the VR4 cost about £140.00 for a pattern part.
The VR4 had the 5 speed box all UK and export model Galants had the 4 speed auto. Only the GDi 2.4 got a 5 speed and that was only for the Japan domestic market never officially exported.
Hope my two posts help you, all the cars I have owned my Legnum was the best by far, everything worked right up to when I sold it. Every time I planted my foot I had a grin ear to ear, the 2.5 V6 would still do the same I am sure, very low end torque engine and loves to rev.