60 series box would be strong enough if it's in good condition to start with and you have some mechanical sympathy (i.e. dont do burnouts fr the sake of a burnout)

the T50 is a great conversion, i run it in my rally car and used to run one behind my A15ETT, but complete install first time (including conversion kit) is about the same price as a 63A box, it's just replacement boxes are cheaper after that

I would say run the 60 till it blows...cause it may suprise you how well it lasts, but 63A would be the most logical upgrade given getting conversion kits from AUS is probably not what you had in mind and celica boxes may not be so easily sourced over there anyway (prices here are about $200 for a T50 and $1100 plus for 63A, the conversion kit for T50 is just under $1000)

JMAC - wouldn't that CA20 box have the shifter 6 inches too far back? i have a gazelle box to off load that has that same problem

D - i think you have said several times that T50 has horrible ratios.... why is that? i have not found this to be the case, better than a-series boxes in the rally car i think, what is your experience with them?

T50
First Gear: 3.587:1
Second Gear: 2.022:1
Third Gear: 1.384:1
Fourth Gear: 1.00:1
Fifth Gear: 0.861:1

60L 4-speed
1.000 1.378 2.170 3.51