F150 and towing advice to pass on

I have been towing on the margin since buying my TT/TV combo in '07. I've put quite a few miles on since then, and while my rig has been competent, I have had my share of bumps along the way. Namely, lack of power. Handling, braking, stability are all very good with this truck. No complaints there. Yes, more payload would be nice, as I regularly use up my GCWR of 15,300, but with only a 4 spd, getting a space at the end of entrance ramps, and climbing steep hills in traffic are still my only complaints. At the time of purchase, a heavier F-250 platform with the same engine would not have bought me anything more in acceleration for a higher sticker price. The newer versions of the 150 with 6spd and more power would probably handle my trailer better, but the same payload package would still be needed for tongue weight. I'll be upgrading in a year or so, and you can bet it will be a 250/350 with the biggest gas engine they make. Been a very interesting and educational 10 years!