I have some questions regarding gearboxes for my '86 Camaro...

I'm planing on swapping my engine. Currently there is still a 305 and a 5-gear trans under my hood.
New engine, that I hope to receive in 1 week's time will be 377 stroker with approx. 450HP.
Rear end is stock 7.5" 10 bolt.

I'd like to hear your opinion regarding my transmission. Will this gearbox hold the power of the new engine? If not - where is it's weakness? I have a possibility to install a TH350, but on my opinion it wouldn't make things better as far as endurance is concerned. Your opinion?

Is it possible that european camaros have different transmissions than the american ones? Mine is from company called ZF that is an European company and it is made out of aluminium, though I heard that american Camaros have cast iron transmissions. Am I wrong? Can you explain a little better?

As I wrote once, I was planing on installing Suburban's gearbox, but I figured out that it doesn't fit in my car...

And another question on rear end. I realize that the one I have currently is probably the weakest I could have. That's why I'm planning on buying EATON Posi performance differential. What do you think about that? Will it hold or is it still too weak? Are there any alternatives that are in the same price rang?

Thank you!