I have a 1945 JD A that I usually pull. Right on for the speed vs slow debate. I'm used to pulling slow since I have JD's.
Now some of it depends on the track too. This particular track is a power track. You usually have more traction than you know what to do with. So you have to have the power to get the job done. My JD A is great in the lighter classes, but falls off quick over 5000lbs. Too much traction not enough gear. I either need more motor, or the gears from a later JD A.
It is kind of interesting, reading most of the threads on here of people that have pulled they said use 2nd Low. For me on this track, 1st Low was not enough. If I had a bit lower gear I could have pulled it out the gate. Traction wasn't the problem, just ran out of steam.