I have a 1988 Dodge Dakota 4×4 with a 3.9 and I did the head gaskets and then I did the timing chain and I have it all set up on the marks and it will just turn over and backfires thru the exhaust

 

I would guess you have a timing issue .... engine is firing on the exhaust stroke and not the compression stroke.

I just looked on rock auto and see your engine has a distributor .... my first guess is it is installed either 180 degrees off .... causing the engine to fire on the compression stroke.
You have a slotted distributor, the easiest to deal with .... you get 2 choices, right or wrong.
Pull the distributor cap, note where the rotor is pointing ... loosen and lift the distributor up just enough to rotate the rotor button to face the opposite direction and bolt it back down and start the engine.

Assuming you did the rest of the work right, installing the distributor is the easiest to get wrong.
Same time it is so easy to correct, almost not worth the hassle to pull a plug and rotate the engine and find the compression stroke, then locate piston on TDC .... phooyey on that.

Drop the distributor in and if it back fires .... swap it in to the other position ....done. ..... this is assuming everything including timing chain is correct.

 

And so I have done everything that everyone has told me and so I have everything on time I think it's just a few tooth off

 

Lets think about this, If your distributor looks like this.


Has a slotted end on it .... this style typically inserts into the oil pump .... when you install your oil pump you have to be very careful to have engine on TDC compression stroke and then install the oil pump.
The distributor just fits in place and the oil pump controls the timing.

The way I understand things, your oil pump was never messed with and is still in factory timing with the engine.
If this is true, the only way it could be off is if the timing chain is installed incorrectly.

The only way forward at this point is to bring #1 cylinder up on TDC compression stroke and work from there.
For example check where the rotor is positioned, and verify that is correct position in the manual. ..... for example my NO1 is at 7:00 O'clock on the distributor cap.
So you set your #1 cylinder plug wire in the correct hole where the rotor is pointing ..... then follow the firing order for your engine to be certain they are all correct.


Yours also is at 7:00 O'clock .... this is what you need to check before you go further. ..... If the firing order on your plug wires is messed up, will also cause this issue.

A tip for finding TDC .... I like to tear off a small corner of toilet paper and cover the spark plug hole on #1 cylinder.
Rotate the engine by hand and watch the paper ..... when it moves, you are on the compression stroke and the compression is blowing the paper around.
Now insert something long into the spark plug hole A screwdriver .... nothing short enough to fall in .... continue to rotate the engine until the object is at full height and the piston is starting downward travel
now back up the rotation and find the highest spot on the piston travel ..... you now have TDC on compression stroke.

If the rotor is not pointing to the 7:00 O'clock position .... You have the wonderful opportunity for improvement, and get to re-install the timing chain properly.
Do not move the engine rotation, this is where it should be when you line up the marks on the timing gears.

Another option is to remove the valve cover, rotate engine while monitoring piston travel ... when piston is at TDC and both intake / exhaust valves are closed .... this is TDC compression stroke.
Rotate the engine one full turn, now intake valve will be closed, but exhaust valve is open .... this is TDC exhaust stroke .... rotor will be pointing at 1:00 O'clock position not 7

Either way you need to do this to verify your plug wires are correct .... if they are, and the rotor is pointing wrong, will probably need to open it back up.

 

I will have to go and see where the oil pump is on marks are right then I will see what I have to do after words and thanks for all ur help

 

I do not want to try and make things more complicated. .... Really is best to have things installed exactly like they should be.
My 1949 Dodge flathead 6, the distributor runs off the oil pump like yours. Whoever installed the oil pump got it one tooth off.
Instead of my No1 plug on the cap being at 7:00 0'clock, it is at 6 O'clock ... so I just rotate the plug wires to start at 6 instead of 7 ..... the engine does not care and runs fine.
It is a common issue on the old 6 cylinders and just accepted practice to rotate the wires to work .... next time we tear the engine down we promise to correct it.

Lets not get lost in the weeds on oil pump installation. Yours was never disturbed by changing head gaskets and timing chain was it?
Main point is to check your plug wires are installed correctly and the rotor is pointed correctly.
If the rotor is pointing the wrong way, it would be because of timing chain installation not oil pump.