Another loose connection to track down. Be sure battery terminals clean and tight as well as the two large connectors inside the front of the underhood fuse box. As well as bolts that hold the fuse links in. Electrical gremlins don't usually "look" electrical.

You can divide and conquer. Battery jumper cable from negative post to truck engine. If things improve, it is in the ground side of the circuit. Unlike your home wiring, the truck just has a hot and frame in most cases.

 

well I jumped from the ground to a bolt on the body and it instantly jumped from 12.5 to 13.5 on the UG took it off and it dropped back ( engine running) so I will be adding grounds

 

On the '98 there should be an earth cable from the battery to the body at the inner wing just below the fuse box.
The OE cable runs from the battery to the chassis ground and has a lug midway along it to bolt to the body. I hate them.
I use a new cable from battery to chassis (#1). A smaller one(#4) from battery to body, then one from the chassis bolt to the starter bolt(#1), eliminating the old starter bolt to chassis woven strap.

 

the only ground I have found in the engine compartment was neg cable on batt ran to wheel well below coolant bottle bolted to wheel well stud then continued to frame that's it none on starter or engine not sure how this thing is running

I added the above noted and will be adding ground from engine to body or frame or both already starts better