I think I may go with 2 of these:-
http://www.t7design.co.uk/products/r...ap7-c-57a.html
If these wont pull through enough air I can add the same in push or a single 16" pushing from the front.
2 10" pulling through are as much as I can get in I think, though there is one last thing I can try and that's stager them diagonally. That way I may be able to fit in 2 11" or 12".
Im not actually ready for these but I want to find the final position for the motor so I can fit the transmission mount in its final position and after I do that I cant move the engine to allow for the fans.