the biggest thing would probably be a set of gt40 / gt40p heads and intake off a 96-01 5.0 explorer/mountaineer
sometimes junked mustangs have exhaust, aluminum driveshafts, and other bolt ons that you can get for cheap (i got a bassani X for $15, aluminum driveshaft for $70, a free tri-ax shifter that came on the tranny, and a few other things)
most junk yards don't look at the car too closely, and a drive shaft is a driveshaft.
Ive heard of a car that had over 10k in goodies it went to the junkyard and got crushed they didnt look at anything. suck for the person that it came from.
like said by Paul the gt4o setup will give you alot of power for the buck.
Some things I heard that would fit, but not 100% positive on all
LS1 Injectors- Rated at 26# but work fine with a 24lb calibrated MAF Sensor
awd aerostar vans- aluminum driveshaft
lincoln mark VIII- i heard they have aluminum radiators with big electric fans
2nd gen explorers, f150s- 31spline limited slip diff, some have 3.73 and 4.10 gearing