Why not just pop the clutch while you're being towed? No need to go through all the hassle of finding a hill to roll down. The occasional 12 volt jump start is probably more dangerous to the vehicle doing the boosting than the one getting the jump. Alternators and other items with solid-state electronics are suceptible to voltage spikes that can do a lot of damage in an instant. Fuel injected vehicles with computers are particularly suceptible, as well as anti-lock brake computers, memory circuits in radios, power seats, and a lot of other sophisticated electronics. The primitive electrical system on a stovebolt truck doesn't have much to worry about on a quick boost start with 12 volts. Justg stay away from both batteries when you make the final connection. There will be lots of sparks, and one flash near the top of a battery can cause it to blow up from the hydrogen it gives off.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!