Offer $200, depending on the year, that is most likely a closed knuckle D44 and is not overly desireable. Verify what he is selling first. You could mod it to be open knuckle, but can be time consuming.
IIRC, the Gladiator never came with a open knuckle D44 front, that axle wasn't installed until 71 and after,but these are not gladiator's, they were just J-Trucks; but people have a tendency to clumping every jeep pick up into the gladiator catagory. I could be wrong, there were a lot of one offs and AG vehicle. you could have had SRW, DRW, solid front axle, IFS etc..