Back then, there really was not much in the way of sealants that were semi-permanent like permagum. Frigidaire used it to seal up the Filtrators and by the time we got them they leaked like the Titanic because it eventually dried out. For the seals on the Filtrators where it was not necessary to ever open them again, I used silicone seal. I don't know if you will need to go into the parts of the freezer you are putting back together. If not, you could probably use silicone seal. If this is an area you will need to reopen and don't want to cut with a blade, there is a product called Moretite weatherstripping and caulking cord. I use it around the gaps in the panels around my window AC units. It is made in the USA by Thermwell Products, Co. Inc, Mayway, NJ 07430 & Sparks, NV 89431.
It is sold in a roll of about 7 ribs so you can use strips just as wide as you need. It does not harden so it can be removed if necessary.
I like the no-nonsense, unpretentious statement on the back, "Can also be used as gasketing material, seam seal, crack filler, sound deadener, insect barrier and general plugger-upper.
I bought mine near all of the air conditioner-installation products at Home Depot many years ago. This year HD did not even sell AC units and I could not find this near the painting products so if you can find a hardware store, that might work. Otherwise you probably will need to go online.
What's doin' with your move?