I parted out a Takara a while back after some consideration. If the bike fits you, grab it with one hand on the top tube and lift it. IF you say to yourself, "OOmph", then part it out. If it doesn't fit you, skip the lift test and just grap your dis-assembly wrench.
Rusty frames have to be damned nice to be worth fooling with or riding around on 'as is" looking like a bum.