Why are the front brakes locking while driving?

Hi, I really appreciate your response and I feel that I'm on the right track, but I hope right now I've not done more harm than good. When I went to adjust the pushrod prior to seeing this diagram the pushrod came loose and was sort free floating inside the booster and I could nearly pull it out if it wasn't for a nut or something on the opposite side preventing it from being fully removed. I was able to get it sitting snug again just by pushing it into place, but I'm not sure that was supposed to happen. I wasn't able to break the rounded nut and spline looking thing on the pushrod with pliers. I can try again though. Is there any possibility it's on the brake pedal side of the booster? Is it more likely an adjustment than a booster failure or is there any possibility the issue is between the MC and brake lines? I installed the MC myself. Seemed to go in fine etc..I'm no mechanic and even the mechanic I typically use suggested changing the booster since the MC didn't fix it (it seemed like all guess work for him) and didn't even suggest any adjustments. Is there any way the proportions are off between the rear drums and front disc's? Sorry to ask all of this but I'm trying to rule everything else out I can think of. All signs point to the initial suggestion though.

Hi,

Yes, basically it locked up the first time really bad when I first took it on the highway. I thought maybe it was from plasti dipping my rims white and not covering the calipers and rotors, figured it got all gunked up. I had new rotors, calipers, pads, hoses put on in the front after that. I installed the MC myself after bench bleeding because the problem remained.I didn't bleed at the calipers because the brakes felt tight still. After doing the MC it had no effect. I drive for about 10min and the they start tightening up and getting hot. I can't find a replacement booster either. I tried loosening that rounded nut at the tip of the pushrod again with no luck. The only thing that works so far is when I remove the vacuum hose and reinstall it, but that only lasts another few minutes until the brakes start locking again.

Hi, thanks for the reply again. This was going to be my next step. Finding one online is very hard for some reason. I think I will send it out to be rebuilt then. I appreciate you taking the time to address my questions!

Definitely will!