95 brake issues need some HELP

[02 f250]

I just bought a 95 powerstroke for a work truck, the truck is in really bad shape but it runs good i knew it needed brakes when i bought it and the master felt like it was shot to. I replaced eveything except the abs vavle, booster, and vaccum pump. Ive bled the crap out of the brakes and the pedal feels really good but as soon as you start the truck and apply the brakes the pedal just slowly goes to the floor and feels like crap again ive read alot of people having issues with this same problem so today I by passed the abs vavle still no results. the vaccum pump looks like it is new and is pulling a vaccum i dont know how much though didnt put a gauge on it but all the vaccum controls work in the truck and when i unplug the booster line the booster has a vaccum in it . ive heard that ford offers a zero lost booster part number F5TZ-2005-CA I hate to drop the money on it if this is not going to correct the problem but this seems like it can be the only thing left that can cause the pedal to feel like and the brakes not work worth a crap. does anyone have any suggestions as to what else i should do so i can have good brakes