My engine wiring harness burned up a couple wires yesterday!

Visegrips! Well now you know. At least you checked first to see if they were holding.
What you did should hold. There are issues with soldered joints, but also some advantages. Make sure they are supported and aren't getting strained or vibrated.

Splicing with open barrel can be done with or without soldering. Open barrel terminals are nice because most have a crimp that holds the insulation and provides better support.
https://www.forabodiesonly.com/mopa...ips-from-the-dodge-ram-service-manual.432623/There are other methods that work. Here's one
https://www.forabodiesonly.com/mopar/threads/clever-splice.447928/
If you want OEM type terminations, the original terminals are almost all "open barrel" terminals. Sometimes available in parts stores, often easier to order them. Same with the open barrel crimpers.

https://www.forabodiesonly.com/mopar/threads/sources-for-chrysler-type-wire-terminals.418908/ You

https://www.forabodiesonly.com/mopar/threads/a-bit-of-wiring-101.506706/#post-1973710272

www.mymopar.com for scanned service manuals, parts books, and Master Tech conference.
Master Technician Service Conference - Chrysler's Training for Mechanics The on-line Imperial Club has a better index of the Tech Conference.

The 1970 Hamtramck Registry Library Page (1970 - 1974) Has Service Bulletins (updates to the parts and service books) and Sales Information (such as options for buyers)

For closed barrel terminals and wire Ancor marine wire products are pretty good. They are carried by chain stores such as West Marine. Some West stores also have reels of marine wire in a wide range of sizes and insulation colors. The wire on reels is sold by the foot. The majority of stores have a more limited selection. They probably also have heat shrink tubing - I always buy from McMaster-carr so haven't paid attention. Mcmaster has oil resistant shrink tubing as well as colors and flexible shrink tubing. Which is best to use depends on the location.

A place to mail order wire in smaller quatities is Wirebarn