Hello All

I have a 56 D4 7U with blade trunnion wear and everything everywhere :) How hard and what procedure would i use to replace said trunnion and components from side plate and C channel arm
Start by pulling it apart and seeing exactly what's worn. Sometimes it's just the trunnion parts, but if the bores are worn too, you'll probably need some machining before reassembly.
The trunnion and caps were wear parts and after market companies sold them even, 40 years ago. Regal Corporation was one that sent adds out back in the day. Who knows Cat might have some lost in the system even. Regal was easy to deal with in the old days if you had parts numbers.
Or drag the welder out. It looks like someone tried that already.