Can a pre computer age motor be put in a '08 F150?

You could but your truck will not be smog legal which means you could not register or sell it.

Getting it properly repaired would be better. Once you get it straightened out it will last a good long time. Computer controlled engines are far better than the old stuff you and I grew up with.

Firstly, you do not want to go backward to old technology, no matter how much you think it is a good idea. Secondly, you'll spend more than your truck is worth doing it. Thirdly, it will not meet smog requirements and will not pass inspection, as Bob said. Fourthly, it will get terrible gas mileage. Fifthly, it will instantly be worth $0 to anyone but you as nobody would want it as their car.

Why can't anyone just answer the flipping question

Of course you can. I have already explained the consequences.

None of these guys are right...Not all states have emission regulations so they only know about their state. That is all they keep harping on. Secondly. new is not always better. Change out 4 O2 sensors twice by dealer after I did it myself but the damn engine light kept coming on. Found a tiny hole in a vacuum line that keeps burning through because of fords ignorant design. Finally a woman mechanic at a 3rd dealer found the problem. But it keeps burning through. It throws off the O2 readings. Truck runs like crap. 4.6 lt v6. And yes you can get it registered if your state doesn't have emission testing. And these that say it isn't valuable are nuts. I am deleting my entire 3 car garage for old over new. I have a 69 firebird....it replaced a 73 beetle. I have a 65 mustang just bought yesterday that replaced my wifes '14 Kia Sorento....and my truck is going bye bye. It is a crew cab 2015 Silverado which is a really nice truck but also a boat itself and can't be parked in less than two moves if cars are on either side and it sticks out of the parking spaces. It is getting replaced by a restored 50'-70 truck of any maker that doesn't have an LS swap. I do not want any more electronics other than maybe coil distr and possibly a throttle body. If I want to take a trip by car I will rent one and that way if there is any problems they get me another. I have always done that even with my new rides.

What do you guys call rat rods. Or all those old fords that have chevy engines in them.