These are the hoses I had made to convert to R-134a. Gary has done this for some other Merkur owners also. He is very easy to deal with. I made the upper hose 42 inches long. He requires the old hose set to do this. He cuts off the old hoses and puts in new one's with a crimp machine. He put adjustable fittings on so that after I had everything where I wanted it I just tightened them down. He replaced both hoses. He didn't add any length to the small hose. He made the long hose 48 inches. It now runs along the firewall and over the battery and and then goes between the front of the strut tower down to the compressor. The hoses can be used with R-134 or R-12. The manifold which bolts to the top of the AC compressor is adjustable. You can push the two fittings down and then turn them to head in any direction that fits your car. Then push them back in and tighten the manifold down. I replaced all the O-rings with R-134 rings just in case I ever switch. You can add about .1 oz's of oil when you change hoses. The hose marking is "Polarseal 12ac134a 5/8" 160mm SAE J2064 Type C Class II 500 PSI WP GL02296 X0000".
The company is called "Auto Electric & Hydraulic Hose", 120 Hansen Access Road, King of Prussia, PA. 19406, Phone: 1-610-265-7334. They also rebuild anything electrical you might need. Gary J. Weaver.
Be sure to support the new hose in some fashion because it is heavier and will put more strain on the manifold pipe and break it. I have had this happen.