First off I'd clean the every living sh1t out of it. Remove rockers, pushrods, etc. Dump some oil all over the place in there, too.
Replace lifters (you can get a cheap OEM set from Texas Speed for 3800 FBody's), clean pushrods and rockers...install new gaskets...button everything up...crank it over...check for leaks and such. Turn off...change oil and filter again. I always do this because any cleaning solution, junky oil, etc...you'll want to get out of there...especially if there is a coolant presence found...which it looks like there is on yours.
If you haven't done it...I'd do valve cover gaskets, plugs/wires, T-Stat, PCV, vac lines (if dry rotted), clean the throttle body well...maintenance, really. If you're close to someone with a scanner or if you have one I'd have it hooked up to check fuel trims as well when you fire it back up to make sure there are no vac leaks.
