Grant's Mosler suffered a 270km/h crash at the end of Conrod Straight after a tyre failure, and is unlikely to re-appear this year.
While the British car is being rebuilt, Grant will switch to a Porsche GT3 Cup S, previously campaigned by the Carrera Cup bound Theo Koundouris.
Having started last season in a Lamborghini Gallardo, the Porsche marks Grant's third GT car in 12 months.
“I have to admit it took me a good few hours to change my driving style to suit the Porsche,” said Grant.
“After driving the Lamborghini and then the Mosler where you have to be smooth to get pace from the car, the Porsche is totally the opposite.
“You have to drive it like you hate it. It has to be moving and bucking to get the times you need to be at the front. I think I'm a little old for the Porsche!”
Grant will have his first race in the car at the Clipsal 500's Round 1 of the 2011 Vodka O Australian GT Championship.
The event will feature a one-hour twighlight race on Friday March 18, with the winner awarded the inaugural Murray Walker Tourist Trophy.
A 20 minute sprint on Saturday will round out the weekend's GT racing.