NO go without Downshifting

Be careful just monkeying around with that kickdown, you could mess the trans up and ruin it. Seems the your motor has a lack of power, a tune up might be needed (does any garages-shops still know how to do that) If you are running points they do wear out and need to be changed once in a while. Just cause the motor starts and seems to run fairly smooth doesn't mean its not misfiring somewhat.