Stock master cylinder doesn't have enough through apparently *shrug*...I just went with the Hinson SuperCars 7/8"s wilwood master cylidner kit.
I'm not running any other wiring for the T56, the vehicle speed sensor is the same, the only thing you won't have is the reverse lockout solenoid switch. I don't have it....it just makes it rather hard to get it into reverse, it requires a good amount of force to override the solenoid but it's do-able.
SR20's are 2.0L double over head cam efi inline 4's, not inline 6's. The inline 6's are the RB series out of the skylines. The RB26DETT is twin turbo'd, and when swapped into an S13 they're usually converted to single turbo for ease of installation because the twins don't fit so well. Twin turboing a SR just seems dumb to me, but if it made good power then why not i guess *shrug*
There's no replacement for displacement.