SOS! Gambler 500! Brake issues!

Hello!
I'm new to anything Chrysler including this forum.
In in need of some sort of brake guru to help ASAP!
I've got the Gambler 500 tomorrow Which is a road rally where you drive a $500 dollar car 500 miles and compete in events along the way. The problem is the $200 Truck's (94 Ram 1500 4x4) brakes are seized in the front! $#!@!
The previous owner said it had a "new" master cylinder, and he doesn't know why they're locked on.
Upon inspection we noticed he never changed the pads in his life lol. The pads wore paste the metal and the caliper piston was the new pad. After replacing both calipers and pads and bleed the brakes were still seized. I tested the booster and it was bad as Well and replaced that to. Now the brakes are WAY BETTER! BUT THEY'RE STILL SEIZED!

Can my master cylinder be bad?
Is this Vacuum related? (Booster hose looks fine and there's a lot of vacuum from the engine side)
What am I missing lol!

Please help as I got the gambler tomorrow morning and the truck still doesn't move because of the brakes.
#FYI truck runs great

Likely the slide pins if he ignored the pads so much. Pull em, clean em with a brass brush, and slather em in brake specific grease/paste

Did you get caliper with bracket or just the caliper? If just the caliper there are two possibilities or a combination of the two. I see it all the time when brakes are overheated and not serviced nearly enough. The most common is the slide pins rusting solid in the pin bore. Take the caliper off and see if you can move them by hand, if they don't move by hand the caliper sure isn't going to move them. If their seized, its 20/80 you'll be able to get them free without destroying them. If you cant, just get new brackets with hardware (often times you must buy the pin and boot kits separate). The other common issue is the location for the pad hardware on the bracket is rusted, that rust decreases clearance and can cause uneven binding (you did use new pad hardware right?), take a die grinder and clean up the areas where the pad hardware makes contact.

In the end, its probably just easier to go buy new brackets and hardware, you can get both sides for about $60 or less last I checked (I only look at duralast not valuecraft or the like)