answered ya own question there dude! Thats the best option really, as from memory the rack itself has the feed lines to the rear rams, that valve block with the electric solinoid in it is just the means to control the flow. also the aus rack is probably about 1-2kg lighter than the jap hicas one so there should be no question!
also as for replacing the rams, i've done this on my gts-x and its all good but still allows a small amount of east-west movement, i think the best way would be to remove the member bushes and get solid rubber or noly ones made up, like the gibson one. ie: