(newbie)1966 C-10 shortbox front end question

[telly444]

hey guys so I bought this truck and the previous owner had no info on it as he bought it already built. So I'm trying to fix/ troubleshoot my front end. The truck sways all over the road and the steering is off. now the truck sits really low with just a 1 inch lowering spring. I ran the part number on the spring, mcgaughty 7387-1 which is a 1 inch lowering spring for a 73-87 C10 So does this mean that my front end has been swapped out from a 73-87? I also have a 73-87 steering column, disk brakes up front and 5 lug all around. I wanted to order some parts but was assuming my truck had a 66 front end. what can I install to help the steering issue and make the more stable/ improve steering? and should I be buying 73-87 front end parts?