Well, according to Pope we are comparing apples to oranges since the heads are not the same between your 84 and my 90.
I have used both Fel-Pro Permatorque and a Mopar Performance HG.
The OE lasted 90,000 miles before it went, it was replaced with a Fel-Pro and we did a "slip and slide" because I needed the car back on the road ASAP.
The Fel-Pro was working fine until I developed an Overboost issue (story for another day) and each time I checked/changed something I would take the car out and go WOT to see if the Overboost issue was gone, well one day the HG had enough and BOOM!!!
That gasket was replaced with a MP headgasket I got online before they were discontinued, I also installed ARP head studs when I installed that gasket.
The MP gasket lasted 6 years (about 21,000 miles) and developed a pin hole leak.
That gasket was replaced with a Fel-Pro which is still in the car.
The last HG was done in Sept 2016, 10,000 miles ago.
To be honest with you, I still use a bit of coolant (1 qt per month from the overflow bottle) with no visible leaks, is it from a HG sealing issue?
IMO and I am not an expert on the early cars with 10mm head bolts I would use the Mopar gasket if I could be sure there would not be any issues with it from sitting on a shelf for 20+ years.
If it were me, today at my age, being retired and not driving much I would just get another Fel-Pro and be done with it.
I am sure Pope will chime in again with more wisdom so we both can learn something. (Not being Sarcastic)
When I was a Chrysler Tech (1995-2010) all Mopar short blocks came with McCord Gaskets so the assumption has to be that they were the vendor for Mopar gaskets.
My Grandfather sold McCord Gaskets in his parts store back in the 60's when I worked with him in the summer.
McCord was bought out by Federal-Mogul who also owns Fel-Pro so draw your own conclusions.
MP W/Pinhole 9/11/16