What would You Choose and More Importantly WHY?

T5s are cheap. Figuring out a bellhousing would be the most difficult part......and it just "ain't" that difficult. And from 85 on up, the first gear ratio in the T5 is 3.35:1. It also has a .68 OD ratio.

3.35, 1.99, 1.33, 1.00, .68. Better ratios than the 833 OD.......at least better for the slant.

Hear are the 833 OD ratios:

3.09, 1.67, 1.00, .73

The T5 has a shorter jump from 1st to 2nd and has a better OD ratio. The slant would respond better with the T5.
T5 has a useless first granny gear, Its very notchy compared to
a A833, if the car has any low end wont need T5 , and an engine of this power wont be able to pull and 0.68 over drive
in hilly roads.