Ahh, now that is different. Yes you can put DOHC heads on that. There are at this time 4 series of 6G7x engines.
1&2 are the G72 series and the G74 DOHC, 3rd being the SOHC 24V engines up to 2001. And the 4th being the SOHC 24V after 2002, The Sport being excluded since it remains a 3rd series till the end of it's sales here in the States.
For what you are looking at there will be two difficulties to figure out.
One is the timing belt, The conversion I did with the tall block uses the 3.0 DOHC belt. This is due to the tensioner being moved further to the passenger side on the 3rd series engines. In your case it will be a low deck engine being converted. We would need to research the belt issue a bit.
The second is the water piping at the rear of the heads, the orientation of the fasteners is different so your existing parts will not bolt to the DOHC heads. I expect a work around could be developed pretty easily.

To add to this, your 3.0 SOHC 24V engine is quite different from the Diamante / 3000gt engine prior to 1996, After 96 the 3K kept it's 1st series engine but with the shift of Diamante production to Australia it then was fitted with the 3rd series engine. This does not mean parts swapping can not happen.