As far as towing goes, regearing is the best performance upgrade you could do. All those engine mods will mean next to nothing if you can't get the RPMs to where the engine makes the most power and torque and only the right gears can do that. The stock 3.55s were designed for highway economy, not towing, and if you have tires even a little taller than stock those gears are crap.

 

I would do the gears.

 

4.10s would work well. The only engine mod that is going to really help out low end substantially is an RV cam.

 

how much weight are ya towing