4-way fuse block terminals have a complete brass body structure and are compatible with any 16 - 14 gauge wire. The terminals tie directly into a fuse block for efficient power out.
It’s been awhile since I messed with a G fuse box, I don’t recall if they used main buss bar on the power side of the fuse with more than 4 fuses, if so, you could make a small jumper or carefully solder 2 terminal strips together.
If the Chevy dash harness is in good shape, it could probably be swapped into the Olds fairly easy. There are probably minor differences, mainly in component location and connector pinout orientation, depending on options. If the Chevy harness came out of a car with idiot lights, there will be differences in the wire location, and some that will need to be added (tach, wire for both the temp gauge and warning light) etc.
The other option, cut the fuse box out of the Olds, and splice every wire to the Chevy box. Your going to need to stagger each splice, or your repair area will be 3 times thicker than the original harness. Use good heat shrink style connectors with the proper crimper.