User @amankd picked up this mod a while ago, and did some updates, but seems to have left the scene, original thread here: https://forum.kerbalspaceprogram.com/index.php?/topic/127736-retrofuture-11312/
It's here! Finally retrofuture space plane parts is available for 1.6.1 and 1.7!
This is still a work in progress. I've gotten it updated to the best of my ability, but will rely on reports from the users (ie: you) for anything