i bought a 1972 sierra grande and have ?'s

[v62go]

its a 402 big block th400 truck with ac, ps, pdb factory gauges am/fm and a tool box built in the bed. its black with white trim and has the same color scheme hounds tooth interior. here's my questions, the truck was parked in the late 90's and what's the best stuff to put in the cylinders thru the spark plug holes to make sure it doesn't break a ring. is there a code anywhere to find out if it has a posi rearend and the passenger door acts like its locked but wont open from either the inside or outside(what's the cure for that?).. thanks for any help.