A saginaw transmission with two grooves on the input shaft should do what you want, it has a 3.11 first gear. Ratios are (1234) 3.11 2.20 1.47 1.00 .
A three groove transmission would give you a 3.50 first gear, which would be lower than your present setup but you may want that.
Most 3-speeds have a 2.54 first gear, so with the 4 speed and the 2.73 axle 1st gear of the saginaw would be very close to 1st gear of the old 3 speed with the 3.42 axle.
