For a truck with 7.18 gears and a 48 X 31 tires which engine is better for off roading?? With the addition of headers and and 2 780 holley carbs, how much horsepower and torque will the engines produce?? Could you please estimate the redline rpm and top speed for the truck??

I would go with the ZZ502/502 personally- has the most power for the $$
With a 7.xx rear gear, your top speed will not be stellar, but who the heck needs an off- roader that goes 200mph??!!
JMO
Good luck- great motor either way