Steering Coloumn: What I did on my 1955 2nd Series chevy 3600 was i bought an aftermarket steering coloumn, w/o shifter, off of Amazon, which cost like $3o0, i have seen coloumns w/shifters on Amazon for like $200 and they are nice coloumns.
Seats: I didn't want to drill holes in my cab so i bought a set of 2002 chevy seats off of craigslist, because the 2000-2006 chevy seats have integrated seat belts. i also got a pair of "Rough Country" Neoprene seat covers that made my seats look brand new. i did have to build custom seat brackets, but that wasn't to hard. I hope that helps you.