There are no DC-8s left in pax service. The last airlines retired them in 1996. Some aircraft of ATI are combi's but only used by subcontractors (military, UN etc). A few others are VIP aircraft.
A few 707s are in pax service; Saha Air is reported to fly 4 on some domestic flights in Iran (local sale only). Inter-Air of South Africa also has reported two 707s for flights to Mauritius amonst others, but there are sightings they were parked in 2001. Jordan Aviation flies one on charters to Baghdad, amongst others. Bin Mahfooz Aviation and Air Gulf Falcon (both based or seen often at Dubai and Sharjah) have two each, mostly used for hadj charters, same with the two of Omega Air.
Romavia and JARO of Romania each have one. They use it for charters (maybe IT to Canaries, Tunisia etc for Romanians), but I couldn't succeed in getting a ride on them.
Hope you might succeed in flying one ever.
nobody has ever died from hard work, but why take the risk?