Towing with a 66 Barracuda with a newer & rebuilt 904
As others all said, add the trans cooler.
I know that hoover dam backup well. Before the bridge I used to get stuck in it coming home from Kingman. 2 to 3 hours from milepost 6 on the AZ side to the Hacienda on the NV side. Hard on stuff to be sure.
Sorry to see such a nice early A leave the area.
B.