The solenoid was part of the emissions package that retarded the base spark timing at idle. Once off-idle, the ign was advanced to normal. Most of the solenoids failed with time, and they were NOT replaced, usually.
If you remove the wiring and contact at the carburetor plus the wiring to the distributor for the solenoid, it'll look "stock" as a 1968 situation did.
If you feel you need the solenoid for cosmetic reasons, just transfer the unit to the new distributor. Easy to do. Just a few screws inside the distributor. Make sure the old unit holds vac, though!
On your distributor, they usually ship with a generic advance curve, so you might check the advance of your distributor at 3000rpm first. Then put the new one in and do the same. Matching what the orig distributor did and then look at the base timing that results. Hopefully, it'll end up at about 10*-12*BTDC.
For good measure, DO check the point gap on the new distributor BEFORE any timing checks happen.
Let us know how it works,
CBODY67