The original wires ran up the right side with the harness and were intended to be held in place by the 'clamps' on the fan shroud (under the radiator hose for the left) and fed through the holes in the hood. There are (were?) clips in the hood to hold the whole harness between the dash and generator etc. The only tricky one is 12V lights have a 'plug' that you need to remove the connectors from, won't fit through the holes in the hood.
If you have a gaffed up harness you can still run it the same way. If the clips are missing from the fan shroud, a wire tie will work.
Regardless, any connection or connector should be soldered. Preferably with shrink tube. Beware of cheap connectors (most any these days)!
When I have a Cub with a home made harness or one that has cracked insulation I replace it. Problems in wiring WILL cause you problems when you least want them.
1971 Cub (Rufus) 1950 Cub (Cathy) 1965 Lo Boy Fast Hitch (Nameless III) 1970 Cub 1000 Loader & Fast Hitch (Lee)