So Ben T is from Alberta. Does he even need a radiator? If he is having overheating problems (according to his iffy gauge) then he needs a cooling system overhaul. If he is going that far and the radiator is proving to be inadequate AND he is going racing fit a larger one. Its not rocket science.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i