Is it possable to drop the pan and change rod bearings in the above with the engine in the car?

 

2wd or 4wd?

Cast aluminum pan?

 

grab yourself a chiltons manual at checker/oreilley auto parts
it will tell you what is possible with the engine installed.
if im correct. as i havnt done it yet if its a 2wd you must pull the engine to remove the pan.
if its a 4wd you must disconnect the frond drive assy and move it forward to pull the pan.

as for the rods and mains the book should tell you what is possible and how to get it done.
good luck. please include more info on truck to get a more specific answer.
let us know how it turns out.