question about very soft brake pedal feel after SN95 conversion. Info please.

Hey guys. About a week ago I finished my 5 lug/ disc brake swap on my 87. I used all parts from a 95 mustang. I also added Russell SS brake lines, and a Summit adjustable prop valve to control the rear, which is the usual additions to make it all work well. I never swapped my master cylinder though, and I wanted to ask about that. When we were done with the rears, my pedal was excellent, nice and stiff with effective braking after 1" of travel. When we went back and did the fronts after a few days, the pedal was really stiff with the car off as it was before. Then we had to loosen one side, reposition the line, and re bleed that caliper. When we finshed that, after an extensive bleed, the pedal suddenly became soft. When I drive the car, I can stop it, but it takes about 3/4 pedal to really feel effect on the brakes. I tried locking them up, and wasn't able to do so under moderate braking, but the car slowed from 40-0 pretty quick. The car stops good enough in traffic if I pay attention and brake gradually rather than hit the pedal at the last second. I'm not really in danger as far as I can tell, but the pedal is bothering me. Alot of sites reccomend that you upgrade the MC to a larger unit when converting the brakes. I have a SN95 99+ MC, but the reservoir broke on it and I can't get another one asap. Should having the smaller MC make the pedal so much softer, or should it be very hard. I thought it should be like a rock to use because it didn't have the power to really move that much fluid. I assume there is air in a brake line, and I need to bleed it out, but before I go tearing it all open again, I want to ask about the MC issue. Any thoughts welcome. Thanks guys.
PS- will my 87 OEM reservoir fit a 99 master cylinder?

Yeah, I just did some reading and found that it is majorly not setup right. I can't use my 99+ MC, because it is a different configuration. My MC is too small to use with the rear disc and bigger fronts. I am going to look for a 94-95 MC, and if I can get one, a booster too so I can have better brake ability. I run an E cam, so I have less vacuum at idle than a stock car, so I should get the bigger booster. I can't believe the car even stops with the way it is now. I hope I am not damaging any of my converision pieces with the current configuration. BTW- I did gut the stock PV, install the metal plug from FMS without the rubber thing, and add the adjustable PV on the line near the pass firewall. I adjusted it as directed by Matt Bobbit's site, and I know the rears are doing something because the wheels are covered in brake dust. Thanks for the help man.

I drive it every day, it's my daily driver. I just take it easy, because I have this issue, along with a little wheel rub I am dealing with. I will be calling junkyards Monday, although I think I should get a remanned one from AutoZone or something. I'd feel safer with that. My friend has the 2-3 port conversion pieces, so I could install it in one day. If I can't get the booster, will it be a big deal?
EDIT- it seems AZ can get the booster too. I bet I can take my Fox stuff and bring it in for the core charge refund. They won't know the difference in the boosters or MCs. They look so damned similar, and I'd rather be dealing with new parts anyway. I think tomorrow after work I am going to pop in there and special order the parts so I can get them asap. I really don't feel like removing this stuff from a cracked up stang in a boneyard, and after core charges are refunded, it'll be like 100.00 said and done.

Ah. My pedal is crazy soft now, maybe I should just save the money and see how it goes.