Any idea what motor this is?

[LBNY_C10]

Bought this 64 c10 recently and I am looking to do a tune up, however I haven't been able to verify that this is the original motor or something put in later. I have been looking for markings on the motor but there is potentially 50 years of grime on it and it is a slow process, additionally searching google for chevy motors hasn't turned up anything that looks exactly like this... Anyone have any idea if it is a 283 or ???

looking to change the oil/filter/drain plug, plugs/wires, new air filter, battery, etc... just looking to make sure I buy the right stuff the first time!!!

New to Chevy and new to the forum excuse my inexperience!!

thank you in advance!!