I'm trying to find a power master cylinder that bolts in the stock location The ones I've seen looks like you need to drill mounting holes in the frame I've seen them before and wasn't ready to buy one. Now that I am can't find them

 

I have not found a power brake assembly that will bolt to the original F2 mounting holes without modification

 

I just installed one in my F2. I bought an under-floor kit two or three years ago that included a basic small diamter booster, a GM-style twin reservoir MC, and a bracket for the booster.
What I learned:
Don't buy a kit that is advertised to fit all Ford trucks that year...they are designed for F1 only. The stock pedal assembly for an F2 has a different 3-hole frame mount than the F1. At least my Long Beach plant-built '51 truck does.
So I had to modify the purchased bracket, and also the length of the kit-supplied brake push rod to make it fit. It was far from plug-and-play, and involved paying a welder to make the modifications rugged enough to have a safe system.
The place I bought the kit from folded up, so i can't even recommend where you can find something to start with.
However, I do see that someone on E-Bay is selling just the F1 bracket for $25 plus shipping. This will still need to have a modified flange installed, but at least it is a start. From there you can get just about any small diameter booster and MC combo to work with it. You'll need to buy three residual valves too and put them inline.
I did not have to drill holes in the frame to install my set-up.

I have driven the truck frame around with the new brake set-up and it seems to work OK. I have 20 inches of vacuum coming from engine, so that part is fine.
I never drove the truck before the upgrade so I can't say how much better it is than just a fully replaced stock non-power system.

Hope this helps.
Tom