I have not seen this one before. To be honest, the guy sounds kind of sketchy to me. The way he makes it adjustable by having everything be slotted in multiple axis sounds good on paper. It would be a nightmare to get all of different pieces lined up and even across the whole frame. I would want to weld them together for the final installation as well.
I looked seriously at the Code 504 kit until a guy I know bought the EZ-Chassis kit:
https://www.e-zchassisswaps.com/2I was very impressed with it and ended up calling Ed and talking to him for a while about their kits. That is the kit I want to get. My long term plan is to use their kit to do a GMT800 swap for my 58. That is a long term and expensive enough project that I am not ready to start it yet though.
