go with a higher gear in the rear, min. 3.73, and maybe check the Q-jet model #, cross reference with;
http://www.cliffshighperformance.com...carb_ID_2.html
your carb could be from CA (emissions) and high altitude. I don't know if emmissions comes into play with yours, but the Q-jet has smaller jets to get past CA. emissions which in turn lowers the HP. I had mine (which was both CA. & high alt.) sent to Jet performance for a rebuild. They increase the jets by 3 sizes.
I haven't broke my motor in yet to pull a trailer, I'll let you know how the Caddy does.
Al.