Front Brake Issue

[Det57]

I have a 69 C50 with power brakes (Booster under the cab and about 5 years old). My front brakes are locked up. I havent tackled it yet. I bought the truck several months ago and have been working on other things on it.

When I go to move it she's locked up in the front. Im thinking possibly collapsed brake hoses in the front or maybe rusted drums??. It does have a new single line master cylinder on the firewall replaced within the last year. This was an old tow truck, and I did check to make sure there was no front line lock on it.

Any other suggestions on what to look for that I may be missing on this old truck? Ive decided to sell it and want the brakes working properly.

Thanks