People were a little shorter on average back then......(really), you can get a kit which lowers the seat rack and lets it sit back a bit farther, lowing the seat combined with the couple of inches extra length works well for most people.
In regards to the brakes, it sounds like the brake linings are the "dime -a-dozen" variety.
It really all boils down to the friction co-efficient....anything greater than .49 will be better than oem in terms of its ability to bite. I would avoid Wagner, Raybestos, etc......this will drive most e-base distributors & big box store "experts" right out of their mind because they either cannot verify this info or you will find the spec is less than oem. IMHO, again look for a CE that is .49 or greater.
With regards to brake linings in general,
Ceramics: They are good but do not develop any more friction than good quality OEM linings (and are used in many oem applications)
Performance Friction & Hawk: Good braking, increased friction but very dirty compared to OEM.
Wagner & Raybestos: a line of products that is 100% marketing and mfg from very low quality/inexpensive and/or imported products with the mfg's not providing any back-up or support on product failures (and I mean real ugly spontaneous, catestropihic failures)
VelveTouch lining- Used for many decades and was the original lining used in all Shelby Mustangs in the 60’s (I personally have used the Velvetouch lining since 1960’s until brake lining production ceased in 1986), then switched to Carbo. Wellman has been the builder of braking linings for all of the Formula 1 race teams for more than 30 years and VT is now available again.
Bendix- TitaniuMetallic™ II, a newer lining (semi-metallic) and although I have not personally used this, I have always been impressed with Bendix brake linings and this particular lining IIMHO would be a low dust, excellent oem upgrade/mild performance type brake lining.
CarboTech Engineering lining, which I have used for about 20+ years and been very happy on multiple full size (V8) cars and trucks. This particular lining has a high friction co-efficient, excellent pedal feel, wears (typically 50,000 to 75,000 miles before replacement is required) and produces less dust than OEM linings.
I highly recommend speaking to them by phone for linings that would be best for your application.
Our own Mustang has been in the family since new (1965) and was the 3rd delivered with 4 wheel disc brakes (from Shelby)...unfortunately the other 2 had major brake failures and Ford in writing to the dealer required the dealer remove all the disc and replace with Drums & VelvaTouch lining.....long story short, since the ground up rebuild (1986/7) we have been running Carbo linings (which are the equivalent as velva-touch) and I am perfectly comfortable taking the car up to 100 mph and hitting the brakes bringing it down to a complete stop, straight & controlled ....as good as any oem disc/drum brake system.