So my truck came with only 2 gauges fuel and water temp and then lights for voltage and oil press and I’m going to get after market circular gauges to mount under the dash but I was wonder if I could still have the warning lights and the after market gauges powered together

 

Yes, you should be able to do that. Simply leave the factory wiring alone and (if you're lucky) find a spot for all the new senders for the new gauges.
Are they going to be mechanical, or electric gauges? Either way, the main issue might turn out to be finding sufficient locations to put the sending units. You might have to get creative.

The thing is, the old sender for oil pressure is just an on-off switch and won't let a gauge read properly. So you either have to replace it with the gauge sender (and lose the light function) or find a new location for the new sender.

The charge lamp is wired into the charging system via the voltage regulator under the hood. Does not use a "sender" per sé so a volt-gauge that you install simply connects to a KEY-ON circuit somewhere. You can access it at the fuse panel, or the back of the ignition switch, OR perhaps the better location would be to find the existing IVR (instrument voltage regulator) behind the instrument cluster (probably attached to the back of the cluster) and connecting the input wire of the new volt-meter to the input wire of the old IVR without disrupting the old wires.
If you're not going to have your cluster out already for other reasons, it might be easier to find a more accessible location.

What other gauges will you be using? Oil pressure? Same thing with the senders, but might be easier to plumb in a "T" fitting and allow you to use two types of senders.
You just have to get creative.

Paul