I hope your not doing a straight trade since your probably getting robbed, although I don't know the condition of your SC300. Pics and estimated value of your car would help, but I'm pretty sure you are on the short end of the stick. Well running s30's can be had for the 4-5k range, a little higher on the east coast.
Also no way in hell it has 59k miles. it probably rolled over once or twice.
Smoking means rings are not sealing, so its burning oil. Ask him to do a compression test. even so it can run like that for a while. I would get a spare block ready though or plan on swapping in another engine( v8, rb, sr, 1j, 2j etc)
I find all the big parts ( body panels, diffs, tranny, engine blocks, carbs) on forums like this.