I think the "F" code comes before the number i.e. FW60a. I have a one of these (overdrive 5 speed) in my ute and have a similar problem- I have already got the box, but It's not going to to cope with extra torque if I want to go for a blower or turbo.

If you are aiming for a decent tourque curve, you would be better off to bite the bullet and go for a celica conversion. Gearbox crossmembers are not difficult to make.

All of the 5-speed a-series boxes are expensive- up to $700-800 for a good one..... the bloke who owned my car before me was offered a grand for the box