Welcome Chris. I don't know much about scratch building frames and such myself, I'm sure there are a ton of people on here that do though. I know there are a lot of aftermarket choices in the way of 3d printed frames and parts.
You have to be fairly specific in your search but there is a ton of great stuff on cults for model cars. Try BlackBox and MCSDESIGN, from there it can lead you down the rabbit hole
Just beautiful. I already have a special place in my heart for old Datsun/Nissans, this build just warms that place! Amazing details all around, great work, truly did this car justice. Love it!