I basically agree, a decently matched car should be able to or like mine under 40 mph you got to drive in second basically making my 727 act like a 2 speed powerglide with an OD gear but not ideal but streetable.
727 2.45/1.45/1:1 x 2.76 = 6.76/4.00/2.76, powerglide+od 1.76/1:1/.69 x 3.91 = 6.88/3.91/2.70