Replacement Power Brake Booster Source for '68 Dart ??

PinkGT said
Is this the unit I need? Is there any other source that might have it without the big shipping cost?

Well, it is listed as being for '67-'76 A bodies, so yes.
Right stuff also carries them.
The Right Stuff | RPB8001 | Brake Boosters & Master Cylinders (getdiscbrakes.com)