Adding a 1400 lb. camper on my 1984 GMC k1500 305 4 speed auto has greatly reduced my acceleration and hill climbing power. To move in reverse on the slightest inclines, I will have to put it in 4 lo or else it will stall. What am I to do? The engine was recently rebuilt and has a rv camshaft, edelbrock intake, and summit quadrajet. I think my diff gearing is to blame for all of this. I only spin 1400 rpms doing 65 mph. Is it expensive to re gear my diffs? Any ideas on the cost?