HEI installed not charging, need help!

Whether a round or square-back alternator, you should measure close to 12 V between the 2 field terminals when the alternator is full on. Indeed, you can disconnect the terminals and apply 12 V w/ jumpers and see if it puts out then. With a few tests, you can figure out who isn't doing their job.

The round-back should have 1 terminal grounded. They do this thru the case, which sometimes works but a dedicated wire is better. The Vreg just applies 0 (min) to 12 V (max) to the other terminal as needed.

The square-back should have 1 terminal at +12 V (w/ ign on). The Vreg applies 12 V (min) to 0 V (max) to the other terminal as needed, i.e. it shorts it to ground (proportionally).

If the Vreg case isn't grounded, it can't measure the BATT voltage correctly (both types) and it can't short to ground (square-back).