I have come to help you out. My pedal was so hard (how hard was it) that I couldnt push the pedal enough to stop the car.
IMO, if you have room for the booster and vacuum to work it, then keep it.
If you do decide to do this, you are going to have to modify your brake pedal no matter what M/C you use. You can keep the factory M/C if you want. I use a chrysler MC with a 15/16 bore. If the master cylinder has a smaller bore than the slave cylinder (caliper piston), it gives a mechanical advantage. The smaller the bore of the m/c, the harder you can get the slave cylinder to push with the same effort on the MC. The thing to watch out with this is that you may not have enough volume to push the brakes far enough to hit the pads and or drums if you go too small on the mc bore or have big bore calipers (or combination of both).
The trick for the pedal is you MUST move the pin that connects to the M/C rod up higher on the pedal to give more leverage. I moved mine an inch up and it made a big difference. I would like to have gone up about 1.5-2 inches, but I would have had a hard time keeping everything in line. You want the rod to push as straight into the m/C as possible. Dont want angles.
I bought the ASP booster eliminator kit for about $70. I think that this kit is ok,but I think it could be better. There is room to move the master cylinder higher on the firewall. This would allow for your brake pedal pin to be moved even higher on the pedal to get less effort.
Ideal pedal ratio on manual brakes is 6:1. I think the stock pedal is about 3.75 :1 or so.
Baer or some big brake company sells a modified pedal and the eliminator kit for 200. I should have bought that.
Also skinny kid makes the kit that rick91gt uses. Jegs and summit both sell kits.
Oh by the way, there is one thing that you give up for less pedal effort, that is pedal travel. You will have less force to push, but the pedal will move farther overall.
Muscle Mustangs and Fast Fords has a tech write-up in the sept 03 issue called rearend remake part 2.
Good info there.
PM or email with q's. I have a lot of good things on what not to do!
i remembered some of what you and Rick were talking about, but did not want to try to regurgitate it on this thread (fearing i would get the info wrong). the gist was that it is kind of a pain to do. thanks for the edumacashion. 
