I have an 85 K5 body/frame great shape (42,000 orig miles). Left town for bus trip, Bro-in-law pushed out of garage with hood/intake removed - filled w/ rain several days. Bro-in-law then covered engine with plastic and returned to garage. Approx 5 weeks later, I get around to finishing engine upgrades and find what is now a boat anchor. Gotta love family. Bought a rusted K5 350/400 silverado w/ ac. Would like to install ac in mine (didn't have before). How much work am I looking at?