if you haven't bought a block for the 8800gt then id spend the cash on a second card as a full cover block will be like £60 and a second card probably similar price
I would second that on the full coverage blocks. Save your money and get VGA blocks and BGA ramsinks for the card memory and/or heatsinks for the MOSFETs. This solution tends to also be more future-proof as you have a better chance of using it on future cards. Besides, the memory and MOSFETs are designed to run at higher temps anyway, and seem to do quite well with heatsink/passive cooling, even when OCed.