Try
www.car-part.com
Put in year, truck older than 1988, select from the menu what you want.
Hint-----Texas has the most 73-87 pickup's than any other state.
GM 1988 to 1991, C-30 or GMC-35 1 tons and 1988 to 1991 Suburbans are the same body style as the '81-'91 truck. Everything from the rear doors (1 Ton and 'Burbs) forward is the same.
I've done the research and checked part numbers in a body shop crash book.
Just my .02
CCDually