Drz110 rebuild questions

So I have a friend who wanted me to look at his 110 to see what was wrong with it. Long story short, the previous owner had it sitting for like 7 years and the piston was seized to the cylinder from corrosion and the head was corroded. The crank and the bottom of the piston were perfectly clean and no play. So I told him it would be cheaper to just buy a new cylinder and head and piston. The big bore kits are cheaper but they are like 143cc’s. To me it seems like you would have to match the cases with a bore that much bigger. Also, they don’t come with a head assembly. Can you mount a stock sized head up to a bored cylinder? I have no knowledge on these little pit bikes. Any information would be helpful. He just wants something to putt around on. Doesn’t have to be a perfectly running race pit bike. Just a yard toy.