IMO.....
Cosworth if you want loads of power, glory and such. But if you want a bargain, you want a V6, and preferably the mk1 shape.
We all know that ford V6's are going as cheaply as they ever will, they have low mechanical running costs, and the sweet, sweet roar of the V6, which, even if if it is a badly designed engine, still pulls 175bhp for very little expense, and gives you almost as much torque as a cossie at low revs. With a bit of cash thrown at it, the 12v cologne can easily get to the 200bhp mark, and if you have lots of money, you'll mebbe get just over 250bhp, but you should have heaps of torque at this point.