Documents archived in the Detroit Public Library Automotive History Collection.
Thanks to Karen Breen for sharing these.
1972_02_27_gmc_motorhome_firestone_press_release_for_firestone_airide_springs
1973_01_03_gmc_motorhome_press_release_anaheim_round_the_clock_emergency_service
1973_02_20_gmc_motorhome_press_release_for_chicago_auto_show
1973_gmc_motorhome_letter_from_general_sales_manager_demo_drive_info_listing_6_michigan_dealerships
1974_02_01_gmc_motorhome_press_release_for_transmode_and_eleganza_se_at_las_vegas
1975_04_brochure_mh-3_glenbrook
1975_09_25_detroit_news_testing_gmc_motorhome_models_palm_beach_eleganza_and_glenbrook
1976_01_brochure_mh-3_glenbrook
1976_01_brochure_mh-5_transmode
1976_02_01_brochure_mh-8_crestmont_birchhaven_23ft_introduction