I might need to wait for re-engined counterparts or B767's
Yes, wait for the re-engined models. Really there is no good replacement for not full DC-8s on long range routes. (Replacement comes out in 1981/82)
Depending on the use you give them. If you are using them for long haul, then the 767 will do great but if you are using them for medium to short haul, the 757 is the best option
What do you think?