Personally, I'd rig the 3 speed auto to stay locked in gear (2nd or 3rd, depending on the course). That way it's not hunting up and down each time you let off the gas to shift the front trans, heating up, and crapping out. Most tracks here can be run mostly in second with a 3 speed, though it depends on your ratios and tire size of course.
Captain: Speedycop & The Gang Of Outlaws -'94 Mark VIII (Least Horrible Yank Tank Stafford '09, NOLA '10) '61 Caddy (Org Choice-NL '09) '63 Tbird (EPIC Repair Failure-Gingerman '10, I Got Screwed-Summit Pt '10, I.O.E. WINNER Stafford '10!) '77 Lancia Scorpion (I.O.E. WINNER Joliet 2010!) '67 Galaxie 500 (Judges Choice-CMP '11)
Future Fleet: 1957 Ford Prefect 1942 Buick 1959 Bugeye Project GLCOAT