brake conversion

Sounds like the push rod for the master is not releasing all the way. Common issue. To check loosen the master cylinder nuts evenly and let them loose see if you can get the front brakes to apply. If so you can adjust the booster for power brake. Manual brakes you will need a different push rod or a spacer on the firewall. See this a lot on conversions there are different pushrods for manual brakes and many mix them up.