After researching, looks like you're asking about L-head engines.
From what I've found, with a bit of guessing to make some assumptions, the first pair of lines refers to the line that is attached to the bottom of the oil filter canister and the edge of the timing gear cover (the return line). The second pair of lines refers to the line that travels from the block next to the fuel pump up to the oil canister (inlet). The differences I've been able to find between the "A" number and the 6-digit number was on the CJ2A online Parts Database (very handy, BTW).
http://www.cj-2a.com/parts_list/index.phpIt indicates that the longer number superseded the shorter number. Same application but I'd assume an upgrade or improvement of some sort. On Walck's website it specifies the length and the type of fittings on each end of the lines. I noted a difference in fittings and a 1.5" length difference on one.
From Walck's listings, the early "A" type fittings had flared swivel on both ends and the 6 digit listing had one flared swivel and one pipe thread.
On my F-head engine, for the inlet line, the block had a brass fitting and the cannister inlet was a pipe thread. The cannister outlet had a brass fitting and the timing cover was configured for a flared fitting.
