I can't find a replacement "Differential/Proportioning Metering Valve" for my '78 F 250 with it's 460 & C6. Mine is beyond repair, & I doubt that I could find 'parts' to even try to repair it.
So my question is: Can I just do with a "Differential/Proportioning Metering Valve" & still have safe effective brakes?
Thank you for any insight/advice/experience you might offer me!

 

I would not trust the brakes without the proportioning valve. It may stop but it also may not when it really matters. The valve makes sure that the correct fluid pressure is given between the front and rears. Its biggest factor is making sure the rear drums dont lock up everytime you brake which could be very bad as well. I know bronco graveyard has them in stock $59 part#22519 just have to get the line adapters. You can always buy a aftermarket as well. But if it was me buy the original less headache and no fabbing to fit a new one

 

https://www.npdlink.com/product/comb...h/148120/50110

 

Tons of them for sale like the one shown from all sorts of manufacturers. Maybe only one or two actual manufacturers and everybody sells the same stuff? I don't know, but there are a lot of them out there.
They don't look like the rough-cast factory Ford parts, but they do the same thing and I believe they also mount the same. Very likely you'll need line adapters though, as I doubt they have the same thread and fitting size as the original factory ones.

But for that, rebuild kits are available too. There is a discussion about this over on classicbroncos from last year where member jckkys (I think it was?) decided to just rebuild his. Pretty sure it was a prop valve too, and not just the old H-block style.
What makes you say yours is beyond repair? Rust issues inside?

All that said, if your truck is modified from original enough, or you drive it more like a car than a truck, I would be tempted to utilize a manually adjustable valve (https://www.wildhorses4x4.com/catego...rtioning-Valve) instead of a factory type proportioning valve. This way you can dial in the amount of bias to reduce the instance of the rears locking up too soon.
Especially handy with lifted, lowered, smaller or larger than stock tire equipped trucks. Or for example one that carries a camper or heavy load all the time could benefit too I'd say.
You would lose the other functions of the combination valve however, including the Brake Warning Lamp function on the dash, and the delay valve (the bit under the rubber cap) that keeps the fronts from applying before the rears.

And something I should mention about the type that caravaggio linked to. They LEAK!
I don't know if they all do it, or just cheap brands, or just certain brands, but we finally stopped listing them on the website separately. I think we still sell a few in the brake kits, and probably still sell on request, but don't advertise them anymore. Way too many come-backs, fix-it-in-the-field complaints, and grumbling about screwed up brand new paint when the delay valve leaked brake fluid on their new body parts.
In the original location, new paint is not a problem usually as it's just mounted on the frame. But plenty of them get mounted in such a way as the drip goes right to the worst possible place!

Anyway, even Wilwood sells a version of that type now, so maybe they're not all bad. But I won't be trying one anytime soon on any of my rigs. Have manual on the '68, going that route on the '71, and seriously thinking about it on the '79 now that I'm talking myself into going hydro-boost and Wilwood (https://www.wildhorses4x4.com/produc...o_Power_Brakes) on my F350.
Contemplating rebuilding the original booster (it's totally worn out right now) but really like the extra room with the hydro-boost setup too. Doesn't hurt that it looks cool either.

I'll probably retain the dash lamp by utilizing an old style H-block with light switch that came on the earlier drum brake trucks.
We'll see though. That's almost half what I paid for my whole truck!

Paul

 

Any proportioning valve for a F250/350 up to 1997 should work fine as long as it's a front disk /rear drum setup. You might need to adapt the lines, IDK, but I'm assuming it'll bolt up.

An aftermarket adjustable proportioning valve would let you customize your front /rear bias.