First things first, fresh oil (HPR30 is my pick, but make sure whatever it is has high zinc for the flat tappet cam) If the oil hasn't been changed for a while it could sludge up meaning you will get the famous oil pickup block the 304's are known for. Also never use oil flush on them, fresh trans fluid (good idea if the trans has been suss), coolant flush (the alloy manifolds corrode badly with old coolant that sat around).
Looks great from the pics for the price, mines got a 185 engine too out of a senator (but that doesn't mean much as the actual engine of a 185 is identical as a standard other than knock sensors and a tune) but at least yours has a nice plate to say so
Also looks like you have one of the only statesmans in existence with a mint leather wheel, make sure you condition it regularly, I had to have mine retrimmed as the previous owner let it dry out and it cracked.