I'm always surprised at those who say the Il-62 was a copy of the VC-10, Tu154 was a copy of the Trident (or 727 - take your pick), but never say that the DC8 "must have been" an espionage copy of the 707, DC9 "must have stolen the One-Eleven drawings", and similar.
Fact is that for a four-engine long haul jet aircraft, there are only a limited number of options. Engines closer to the centreline gives less chance of an engine failure getting out of control, as 707/DC8 operators, especially on training flights, found out only too well. The Soviets never did a jet with wing-mounted engines until the Ilyushin 86 widebody came along in the late 1970s, so going for fuselage mounted engines should not have been that much of a surprise.