Two small fans do not add up to one large fan, funny as that might seem. For example, two 12 inch fans will not put out what one 16 incher will. But I understand what you are saying about space issues.

I had a radiator built one time that had two small puller fans mounted on a shroud, they were staggered. It also had two holes in the shroud with rubber flaps over them so that going down the road the air would escape the shroud and flow through better.

If you have no shroud now, that would be the first step, and putting two good fans, like Spal brand, will help too. But it may be that that blown engine just needs more cooling than you can fit in there. Locally there was a prostreet vette with a wicked blown motor in it, and he would trailer it to shows and even driving into the show off the trailer it would spit all the water out of the radiator.

The aluminum radiator will help too, especially if it is a good brand.

Don