I would pull all the spark plugs and look very closely at all the ends to check for condensation and rust, if that is good then try rotating the motor over while priming the oil pump. If that goes good, no noticeable tight spots, then look at installing it and running it. Be very careful on the timing, jetting and gas quality with that unknown compression ratio
I'm in the middle of building a 413 H.D. truck block into a pump gas 463 C.I. motor(4.250 bore with a 4.150 stroke) for my 1963 Plymouth Fury. I'm hoping it will make a little north of 450HP with the right cam , 440 Source Stealth heads and a Eddy RPM intake with around 10.0 to 1 compression ratio