First you have to determine if its a 1st series or 2cnd series because its a 63. They had different frames in 63 as the 4x4 frames were a change over mid production year for 63s. Also always mention Chevy VS GMC when asking ? as GMC is different . I was able to find a previous post of your 63 Chevy with 292 K20 which makes it a second series being a 292.
GM Part number for a 1963 2cnd series FRONT cable 4x4 3824111 is 85 11/16 long and just so happens to be listed on ebay
https://www.ebay.com/itm/36434397653...Bk9SR96Y_NaoYg
GM Part number for 1963 2cnd series REAR cable 4x4 3824114 GM parts book does not give a length but its for ALL Chevrolet 1963-1966 K20 4x4