1997 Ford Aerostar Aerostar Low heat on both front and rear

Sounds more like restricted heater cores.

What do the heater hoses feel like at the heater cores? Hot to the touch, same temp?

Okay good.
Lets look at the probablity of air pockets. I think you have a stubborn one. Raise the front of the van up 3+ feet or as high as you can get it. Add coolant a few ounces at a time. Keep reving up engine, lettling it come back to idle. May take 50 times of this slow procedure.

There is a tool that snap on makes. Prolly others too that attaches to the rad and puts a vacuum on the system to pull the air out. The aerostar can be a real stubborn one to bleed. The engineers didn't worry about that when they built it. I'm pretty confident that you'll nail this thing if you get the air out.

I still think there is an air pocket in the cores.

Remarkable how much the temp came back for you by blocking off the air intake duct.

I'll look for the info you requested and update when I do.