What Disc Brakes to Use

Could'nt tell if your brakes are power or not.
If manual,Your not using semi metallic pads are you?
They will NOT stop untill VERY hot!! and then not very well!!
Ford actually had a service bulliten on this in th 80's on escorts,rangers and mustangs saying not to put mettallics on manual brake cars.
I had to special order organics when I converted my 66 Cuda as no one locally stocked anything but mettalics for '73 up Mopar disks.
Hope this helps.

Semi metallic pads are not an issue with manual disk brakes, technology has come a long way since the 80's. I have over 30k miles on 73+ disk brakes on my 68 Barracuda with a manual master cylinder. Takes a little more foot pressure but not excessive than it did to get the initial bite compared to the 9" drums (drum brakes by design give more initial bit due to their self energizing design) that were on the car but stops with the same level of confidence as either my late model pick-up or my wifes PT Cruiser. I would stay away from organic pads; they may have more initial bite at a lower foot pressure but they will fade much faster when they get hot reducing your ultimate stopping power compared to semi-metallic.

When I did the conversion the local parts store only had loaded calipers in stock so I went with the pads that came with the calipers . I was more than happy with the braking but they squeaked at low speeds. I replaced the pads with Raybestos PG+ pads which are a premium replacement pad. Besides getting rid of the squeak there was a marked improvement in the stopping power.

My recommendation before you go taring the front end apart to change the brakes try a premium pad. If this was a cheap kit they likely came with cheap pads. Something from EBC, Hawk or the like will likely make a big difference. TireRack.com sells a wide assortment of high performance pads. If the kit uses GM calipers you should have a large choice. I always get pads for my daily drivers from these guys and have never been disappointed with the performance improvement.