Looks like '66-'68? Sounds like you need the original tires for these to get the exact year.
From the CABE
Ultimate Sears Spaceliner Reference.
PAINTED MODELS
NOTE: Specifications common to all of the painted models, and therefore not repeated below unless otherwise noted for clarification, are: tear drop double reflector on rear fender, no springer fork, no front truss bars, no horn, no tail light or rack reflectors, no seat crash bar, no chain ring cap. Details that vary by model number are shown below.
Men's / Boy's
46303 (1964-68, 26", Straight Tank, Men's, 1-speed, 1 round rear fender reflector in 64-65 was changed to a tear-drop reflector plus 2 rack reflectors in 66-68)
46343 (1964-68, same specs as 46303, 2-speed)
46323 (1964-68, 24" with same specs as 46303)
46305 (1966-68, 26", 7-Tank, Men's, 1-speed, tear-drop reflector, 2 rack reflectors)
46345 (1966-68, same specs as 46305, 2-speed)
46325 (1966-68, 24" with same specs as 46305)
Woman's / Girl's
46313 (1964-68, 26", Straight Tank, Women's, 1-speed, 1 round rear fender reflector in 64-65 was changed to a tear-drop reflector plus 2 rack reflectors in 66-68)
46353 (1964-68, 26", same specs as 46313, 2-speed)
46333 (1964-68, 24" with same specs as 46313)
46315 (1966-68, 26", 7-Tank, Women's, 1-speed, tear-drop reflector, 2 rack reflectors)
46355 (1966-68, same specs as 46315, 2-speed)
46335 (1966-68, 24" with same specs as 46315)