the 9800pro has more optimizations... the pcb is longer meaning there are additional capictors probably that are being used to clean up signal chatter and 'seepage'
IMO
the 2 cards ARE different sizes but since the r350 is a refresh of the r300 core.. it should and does share many similarities...
the 2 cards are NOT the same... they have similarities... and can be considered members of the same family... but AFAIK there is no way to make the r300 run like an r350... the design and the tolerances does not allow for this...
keep in mind that the memory used for the r300's is rated to run @ around 400/400 rather easily... stock... (maybe a little high estimate... but for sake of argument lets leave it @ that)
the design of the board... and the tolerances do not allow the card to be clocked too high stock... if it is.. there are artifacts and/or the system buggers during benches...
the r350 has a reworked pcb to allow for higher clock speeds... and tolerances...
the r350 with 256mb DDR II coming out soon will be on a 0.13 micron process design and should be a very interesting card
the cat 3.2 is basically the official driver set for the 9800pro... cat 3.3 will increase the r300 based cards performance as per the catalystmaker (can be found @ rage3d forums) who said that while working on the drivers for the 9800pro... they found areas to improve the drivers for the 9700pro...
good news all around...
to sum it up... 9700pro != 9800pro.. therefore I don't think mods... software or hardware... will make the r300 into an r350... AFAIK...