318 Build? Help!

It don't take too much power to tow, just with smaller engines you might have to drop it a gear or two to get in the powerband, unlike a diesel that makes it's power at rpms that happen at general road speeds so no or little down shifting required.

Your probably gonna be in the 2500-4000 rpm range most the time, hp is 50% of torque at 2626 rpm and 75% @ 3939 rpm. With a decent 318 should be able to make 330 lbs-ft @ 2626 rpm so 180 hp and around 360-380 lbs-ft @ 3939 rpm so 270-285 hp.

Sounds like your plan is on the right track just don't go crazy with cam and everything should be fine.