I did the same thing for a SS conversion. I found an old Kabuki hilltopper 12 in horrendous shape at a pawn shop for 40 bucks. handlebars/frame were fine. Found another crappy Hiawatha dimestore POS that had decent brakes and some other components I needed(lady sold it to me for $5) and an Araya front rim with a decent hub. Luckily I found one of those Ebay Eight Inch conversion kits with a 27" back wheel locally from a girl who didnt know hers was fitted for 700c for $50. Spray bombed the frame light pink and threw some white bar tape on there.
Man does that think look like crap. But no one has ever had the desire to steal a pink, multicolored, mismatched bike in my crappy neighborhood. If only they knew how well it rides. I dare never post pictures on C & V because it would probably be torn apart.