the old '87 with 300k on it has sat for nearly 2 yrs
before starting, i was gona remove the plugs and squirt some Marvel Oil in each cylinder, let sit a week

ANYTHING else i should do before putting a new battery in and cranking?

 

Drain the old gas. Tank should have a drain plug.

 

turn the engine over a few revolutions by hand with a big socket wrench on the crank bolt and the plugs out after you let it sit with the oil in it.
My buddy and I started an 81 that had been sitting for 15 years after hitting a tree and it ran like a top. Just put new gas in it, threw in a battery, pulled the bumper away from the passenger tire and drove it home!
Didn't have time to soak it with oil, the owner said it had to go, needed a tow truck, and we could have it if we moved it that day. He about crapped his pants when we drove it away 2 hours later after we left to get fuel, battery and chain and spent less than an hour working on it. The only thing we wanted was the rust free bed, cab and the engine that had just been replaced 15K miles before he totaled it. (the frame was badly bent.)

 

Just spray some brake clean in the intake and Staht the Bastahd

 

My truck sat for 12 years so I bought plugs for it, scooped petroleum jelly/rust out of the tank, changed fuel pump cause I soon realized it was dead. Almost started to run just couldn't make it really fire up fully. Looked in the air box, something had made a nest in there so I pulled it all out, vacuumed it, put filter back and it ran but still felt like it was struggling. Pulled out the air filter and it started in faster, fully and idled purrfectly. Dropped in a new air filter and have been swapping out fuel filters every 2 months cause the tank is still filling filters packed full of rust every 2-3 months. I just had to swap the clutch slave, new exhaust gasket, and some used tires to see how well she was willing to roll down the street.
I hope your rig comes back to like as easily.