Looking for a new headliner

Does this need to look factory correct? If so you will have to locate an original.
If close will suit your needs it can be done at home. (You said you've made your own panels)
You will need to remove panel from car.(this is a must for professional results)
If it has cracks or missing pieces you can repair them, try not to do more damage during removal and handling. 40 year old card board can be fragile.
If the fabric or vinyl cloth (if it has any)is coming loose from the panel it needs to be removed
If it is still fastened secure, leave it alone and cover over the cleaned (no armorall) original.
If you have tears or splits in panel they can be repaired with aluminum furnace tape.
Your repairs will need to be smooth to be undetectable. Keep creases out of tape.
Warped or sagging panel can be reinforced from the back side if clearance on the back side allows by taping or gluing paint sticks or something similar to the top side.
Now you need to choose a new cover material. If you use the modern foam backed knit type it will be much more simple from here on out to get smooth results. It is available from any upholstery supply at a very reasonable price and many colors to choose from.
If you wish to use vinyl you probably should PM me for more detail than i care to type here.
Or take to a upholstery shop as this would likely challenge most skill set and sanity without some prior experience. Your call on this. I have found some folks can be good at things and others pretty much just make things harder to repair than they were in the first place.
You will want to use contact cement. I spray the glue thru a gun at my shop but it can be brushed. Coat the panel first and let dry. Then coat the fabric and allow to get nearly dry or tacky. Drape new fabric over panel being careful not to press it down anywhere you don't want it to stick. This is a one shot to get it right or start over with a new piece situation.
Press down with very light pressure starting in the center and working towards outer edges taking care to not allow any wrinkles to take a set. When you are satisfied press firmly over entire area to set the adhesive.
You can flip it over and glue the edge over the back side if desired.
This is kind of a brief summary of the work involved but with patience and careful attention to detail a first timer can have good results and save yourself about a $100.
If you want a little more detail than I can stand to type here PM me, I don't mind helping out with any upholstery advise. Hope this helps some with their mopars.