Hi jimg1au,
If you are trying to decide between a 500 and 650 , you will be always chasing a 650 ,at least to the first corner,on a 500 ,you'll have a bigger smile on a 650 even just listening to it ,still a great range of go fast bits for 650 unit motors,
oh yes I just happen to have a excellent set of matching cases from a 63 6T, first unit year, email me