For the T5, it's not necessarily a matter of HP or TQ, but if you get the tires to hook with say 400+ RWHP and are trying to launch it at a drag strip, eventually the T5 is gonna break. If you plan to street drive it and let the tires (traction) act as a circuit breaker it will be fine even with boost... but if you have traction and lots of power, it won't last. There are companies out there (Liberty I think??) that can build up a stout T5 that can handle the power, but at the prices it takes to do that it makes more sense to get a Tremec most of the time.
As for the brakes, LMR sells kits with everything you'll need if you want to go that route. It's not "cheap" but will be all inclusive and new parts. The only things you'd still need are a set of 94/95 front spindles and 5 lug wheels/tires. This is a proven setup for the foxbody cars that does not need anything special and will be just as good as most of the fancy big brake kits out there. If you want to get a little more fancy there is the option to use
Brembo 4 piston calipers from a Cadillac ATS for about the same price as the SVE calipers which is what I put on my car but you have to be aware of wheel sizes there and use different rear calipers and use the proper master cylinder to get the right balance.
This link shows you all the options and the steps to build your kit,
https://lmr.com/products/fox-body-5-lug-conversion-cobra
Below are the link's I'd use if it were me (assuming you have 28 spline rear axles).
1993 Cobra power brake booster will restore the proper function of your Mustang power brake booster!
lmr.com
Complete your Fox 5-Lug disc conversion with these Moser 28 spline 5 lug axles with SN rear flange!
lmr.com