Pcv system on carb setup

That's one way to do it. Just ask them for a stock PCV valve for an '85 Mustang or anything that came stock with a 351 might not be a bad idea, but knowing Ford they're probably the same part. On the stock setup one side had a breather and one side had a PCV. On some cars this isn't enough and you'll still leak oil out of your valve covers...mine does. You can also look into getting an exhaust evac system which uses two weld on ports on the exhaust to create a vacuum that pulls air out of the valve covers. They're not super expensive, i think the last time i looked you could get a setup for about $40.

That's more or less how Ford did it on the carbed cars. There's really nothing to "figure out" here...just do it like Ford did it, which is basically how you put it. I never had a line coming from my breather side to the air filter though, it just vents out. What i was saying though is that even with doing it the "right" way, you may still leak oil out of the breather or from under the rubber grommets. I've tried bigger size PCV valves, i've tried different breathers...nothing really made much difference. Now i just run a big hose from my breather side down to a catch can hidden in the bottom of the engine bay which gives that leaking oil somewhere to go. On the factory setup there was even a filter in the air filter housing that was there to catch any oil that made its way through...so even Ford knew about this issue but i guess on bone stock engines it wasn't as big of a deal.

I have a breather on drivers side valve cover and a straight up PCv valve in the passenger. It routes to a clear plastic fuel filter, and then to the front of my carb. This works very well and the clear fuel filter catches the oil residue in it that would normally clog up your intake. Kind of a poor mans catch can