Put in the DUI distributor yesterday in my '79 CJ7 with 304 v8. First time for me installing a distributor but everything went smoothly and it re-fired on the first crank. Noticeable increase in acceleration and power. Don't know if gas mileage will improve.
Only snag was having to grind on the hold down clamp to get it to fit the base of the distributor.
A bit expensive but worth it in my opinion. Went with Live Wires as well.
Set the plug gap at .50.