Luggage rack dimensions?

Hi,

I'm trying to determine the dimensions of the roof top luggage rack as fitted to the GM B body wagons from 1977 to 1990.

I'm looking to purchase a luggage rack cover and want to ensure it will fit within the two out chrome arms.

Can anyone check their's and post a reply?

I'm out of the country so can't get to my 1988 Oldsmobile Custom Cruiser.

Thanks in advance for any help.