serjtag, avrdude and Arduino Duemilanove

Hi,
I've got Duemilanove ATmega 328, Windows XP.
I want to change MCU to cheaper ATmega 8 at this board for my simple experiments.
I added 4 programming pins to the board and made a cable for ICSP programming of my board.
The trouble is how to config serjtag for Duemilanove in avrdude.conf ?
It must be something like

programmer
id = "diecimila";
desc = "FT232R Synchronous BitBang";
type = ft245r;
miso = 3; # CTS X3(1)
sck = 5; # DSR X3(2)
mosi = 6; # DCD X3(3)
reset = 7; # RI X3(4)
;

Then I gonna do:

avrdude -c duemilanove -P ft0 -p m8 -B 4800 -U hfuse:w:0xca:m -U lfuse:w:0xdf:m

avrdude -c duemilanove -P ft0 -p m8 -U flash:w:ATmegaBOOT.hex

avrdude -c duemilanove -P ft0 -p m8 -U lock:w:0x0f:m

How can I do the task with STK500 board if this method fails?

Please help!
Thanx!