I prefer a kickdown switch, but back in the 1970's they were almost impossible to find. A toggle switch will work if you drive it like a two speed axle. You flip the switch and momentarily let of of the gas before you step down on it and the OD will shift just as smoothly as with a kickdown switch. I started driving trucks with two speed axles over 60 years ago and put over a million miles driving a two speed Eaton or a 3 speed Eaton which is actually two 2 speeds running one in high range and the other in low to get an intermediate speed. Using the clutch allows them to be free for too long and this is what tears up two speeds as well as overdrives. Now kickdown switches are being reproduced and can be bought for around $30. So I would no longer recommend using a toggle switch.