What are better for Drag racing, hydraulic or gas rear shocks, for a stock mopar leaf springs susp.? Thanks.

All(automotive) shocks are hydraulic. Gas shocks use a gas charge in addition to the oil (hydraulic). The gas helps suppress the foaming that is created within the shocks during use. Foam puts bubbles in the oil and prevents the shock consistent dampening performance. So that being said I don't believe most Drag only shocks are gas shocks where as roundy round or street shocks would be. Although the drag shock does do a considerable amount of work each pass typical drag surfaces are considerably smoother than most street and oval surfaces (strokes /per minute)
If this is a Drag only application I don't believe you "Need " a gas shock

Is it a street/strip car or drag race only car ? I am still very old school as on my 63 street/strip car I use SS springs and the older MP hydraulic longer shocks for SS springs. They work fine for what I do which is mostly street driving and it has pulled a best 60 ft of 1.50 running 10.70's. Not going to set no world records but it works fine for what I do on a tight budget. Ron