2-speeds generally have two ratios- - - -"slow" and "really slow". I'd suggest keeping the 4.11 rear end and adding a good gear selection with whatever transmission combo works best. Pay close attention to the ratio progression between gears, as Detroits really hate to lug down.
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!