A local junkyard has a wrecked 1988 Cadillac Brougham with a supposedly good 307 for $375. The engine in my LeSabre runs fantastically for what it is. It burns/leaks oil and has a rod knock, but it keeps going and going and going. Someday, its going to quit going, I've accepted that. But if I can grab essentially the same engine, tear it down, make sure everything is copacetic, and reassemble it, how difficult would it be to yank the old motor and drop the "new" one? I'm most worried about transmission (THM200-4R, shouldn't be a problem) and emissions devices. We dont have smog testing in this part of the state, so would bypassing all that crap be an option?

This is something I happened across today and likely wont happen until Spring due to money/time/weather. My biggest concern is how long will it take to get it done, if we dont get a 3rd car, the LeSabre will still be my daily driver.

I'm not sure exactly how long it will take. Alot of it comes down to how much of the "crap" emissions stuff you keep. The transmission will be fine. I've had lots of 307's, and we always yank all that stuff off, plug off the EGR, get a mechanical quadrajet and a vacuum advance distributor and yank the computer, and cut off the converter. It would make the swap easier and way fewer potential problems, but it also will kill the gas mileage, but the performance improvement is astounding. Mine all had the above done and true duals with Flowmasters and a neck snapper TH400 with a 3:73 out of a Monte SS, so I got like 5mpg. LOL Its a good deal if the engine is good. If it isn't and you're going to end up rebuilding and still want to yank all the emissions junk off, you could build an old non-emissions 350 Rocket or something.