Unfortunatly if the heatsink/fan is too big, the CRT is going to get in the way, because it sits around in that area. So removal of the block and part of the steel frame may allow some room for a fan, but not too much.
MacBook 2GHz Intel Core 2 Duo w/ 2GB DDR2 RAM & 120GB SATA 5400RPM HDD
Canon Rebel XTI
Google Cr-48 Beta Laptop