Hey Hussein. Generally speaking...in your case, when you get an engine from the wreckers, you will NOT get the exhaust manifold, alternator, or starter. Other stuff like coil packs, mounts, intakes, etc will be hit and miss....wiring bits may or may not be chopped or intact....
They assume that in 99% of cases like yours, you have an internal engine fault in a complete car. And can thus re-use your existing manifolds/alternators/wiring/hoses/mounts/etc when replacing the engine. I have already explained about the exhaust manifold. Alternators and starters they can sell separately to end users or in bulk as cores to the rebuilders - again money in the bank.
Any other ancillary they either sell separately or - as time is money to them - they will just cut a wiring harness or engine mount if it makes removal quicker. They just assume you can re-use your existing ones.
Which in most cases is okay. but a real bummer if you need to use the the engine for a swap like K20 into X1/9. For that reason you will find most of the JDM engine places sell it much more complete.
Funny story - i recall years ago going to the wreckers to get a rear trailing arm for a Volvo 140 ( remember those ? ). They wanted like $20 for it. Bolted on the body with one bolt, and onto the axle with one bolt. Yup...watched the guy just torch through the bracket on the body - hey no big deal on a wreck - and then instead of undoing the bolt to the axle, he just torched the bracket on the axle itself. Thus rendering the axle useless.....