NorthStar Horizon restoration question

Hello all and thank you for adding me to the list. I am in the process of restoring a NorthStar Horizon machine. The boards in this machine have a significant amount of flux residue on them - it certainly appears that this particular machine was constructed from a kit. My question is about this flux - should I be removing it as part of my cleanup, or should I leave it in place? I know that this isn't a super-collectible machine or anything, but I've never come across this issue in any other machine in my collection, and I was wondering what the general consensus was. I'm perfectly aware of the corrosive nature of the flux and how to remove it, however this flux has been there for 35+ years. Thanks in advance for your thoughts. Ian