I'm getting into hardmodding Radeon 3870s. I have 5 of them, 4 are in a rig for CrossfireX. One spare.

I will be upgrading capacitors that fit in the same place as the existing ones. I am:

Upgrading the 180uf 16V to 330uf 16V
Upgrading the 820uf 2.5V to 2200uf 2.5V (and filling in one empty one near the top of the board)
Installing the "missing" 6.5mm x 6.5mm SMT with 16V 220uf
Also installing trimmers for Vgpu and Vmem.

I'm curious about the four large square items on the board. They are labeled R47 738 M3K. I might want to replace these with something a little larger and more stable if it makes sense to do so. I have about 1.5mm to 2mm of clearance under my Koolance water blocks for these. What are these and what are the specs?

Thanks...