440 swap in 66 cuda

at a minimum, tie the front and rear-- this is the most common, search "subframe connectors". you can buy or build them.

from there it depends on what your plans are with the car. just a cruiser and bruiser, i don't know i'd go much further than that. if competition, i'd be rethinking from the ground up.

either way, i'd reinforce the K member for sure.