It will turn over but will not crank, changed fuel pump, fuel injectors, crank shaft position sensor, plugs and wires, and I have checked the security system, don't know what else could be wrong, I've put in over 1000 trying to fix

I assume you mean, it cranks over, but the engine does not fire....

4.8 or 5.3? Well, makes no difference as far as spark and fuel are concerned....

Have you scanned for codes?

Checked fuel pressure?

Checked spark on all cylinders?

Checked for injector pulse on all cylinders?

Diagnosis, saves a lot of money.....

I'm getting spark on all 8 and I have plenty of fuel pressure as well, don't know how to check injector pulse an it'* the 5.3 and yes ive scanned for codes nothing has showed up

Define 'plenty' of fuel pressure? These engines won't run below a specific fuel pressure. So when someone pushes the little schrader valve and sees fuel squirt out, they automatically assume they have "plenty".

When we ask what the fuel pressure is, we expect that the result should come from an attached gauge to the fuel rail. Not a screwdriver to the schrader valve. Sorry to sound like an old codger, but I've been here for quite some time and have seen the tricks of online diagnosis where people say they did do something, but didn't.

I think those 5.3'* are spec'd above 48 psi.

didn't put a gauge one it but it shoots out pretty hard way more than it did withthe old fuel pump, I work off shore so I'm not actually able to work on it myself but it seems every time I change something out or whatever it doesn't fix it, getting close to being tired of sinking money into it

We need to know what the exact fuel readings are in psi.
How many miles are on this vehicle?
If it is higher mileage, a compression test would be a good idea, just to eliminate that too.

it has 170000 miles don't know exact number and I don't have the money to keep putting into all these test this truck has driven me broke

What we are trying to tell you is, proper diagnosis, could have saved you a lot of money....

You only replace a fuel pump and filter, if pressure is too low......you don't even know what the pressure was.......a gage is need for pressure, as Mike has suggested........and sometimes fuel pumps are replaced, that are still good, because of a bad ground in the circuit....

You have spark....did you have spark before replacing the crank sensor? If yes, the crank sensor was not needed....

Why did you replace injectors before checking for fuel pressure and injector pulse? Did someone else diagnose this and do the work?

With 170K miles, you could have compression problems(as Soft Ride said), so a compression test may be in order........

You say the SECURITY system was checked out......exactly how and by whom? A security problem could kill the injectors.....

One of the simplest tests you should have done first, is spray carb cleaner into the intake and then attempt to start the car....if it started and continued to run as long as you sprayed, you would know you had a fuel delivery problem.....either not enough pressure, or the injectors are not firing.....

Agree with the guys above, however, thinking what I would do I might have an option for you.

First: Definitely do the carb-cleaner test. Listen for it to huff or puff beyond just plain old not even trying.

The thing I thought of:

I have a 2001 5.3 with 296,000 miles and compression isn't an issue. Assuming yours hasn't been through something horrible that we don't know about it probably has enough compression on enough cylinders to start. With all of the parts you replaced it will be reliable for a long time once we figure this out.

On a still (non-windy) day, turn it over for at least five seconds. Quick run over to the exhaust pipe! Do you smell raw gasoline?