90 dim tail lights

[my90k5]

I have a 90 full size Blazer all original, no rewire. Everything works fine except the dash and tail lights seem really dim. I know about the headlight mod to keep from loading the dash but would this cause the tail lights to be dim as well?

I did find the chassis ground broke loose at the battery end but no difference after repaired. Is this common? or has anyone had this problem?

I'm thinking of running a separate ground wire to the rear to see if maybe I have a bad or loose ground wire.

Any thoughts would be very appreciative,
Thanks