I had the carburetor rebuilt in 1994 and again in 2008. In 1994 I remember purchasing the kit and especially the accelerator pump, and then had a mechanic do the rebuild. Someone else had suggested the accelerator pump as a possible cause for the hesitation. In 2008 the carb needed work and I took it to a Lincoln-Mercury dealer; they had the carb sent out for a rebuild. The hesitation didn't change either time. I suppose it's possible the rebuild wasn't done right both times. When the dealer did it in 2008, I know they sent it out to a reputable shop; they didn't do it in-house.
As requested, here are some interior photos. Alas, it isn't flawless, inside or outside, but it's not too bad. It needs new carpet, front and back. The front carpet was obviously replaced at some point in its life; the color isn't quite right. Some of the stitching on the driver's side seat bottom is coming undone. The vinyl seems to be in good shape, though.
The original dash pad was cracked at the speaker opening, which is not unusual. I found a black pad in perfect shape, had paint mixed and sprayed it myself. The color is ok but the texture isn't quite right, so eventually I'll re-do it or send it out and have a pro respray it.
Here is the way-back. I was lucky to find the side-facing seats in a junkyard Colony Park in the correct color; I think it was a 1973 model. It was lying on its side which made dis-assembly a little tricky. I was also able to get the latches which are necessary to hold the seat backs up and didn't come on my 6-passenger. I still have to install those sometime. I didn't have time to get the seat belts and regret that. I know there is at least one company that can create seat belts if you provide the buckles and latches, but it isn't cheap.
well ...if it aint the pump...then swap carbs....they'r cheap ... www.rockauto.com otherwise...it could be that the timing is out ....that will give you the same hesitation btw...nice guts too