On my SA 425, I installed a Pat's Quick Hitch. I had to make a trip to TSC to buy a longer top link. When I installed my hydraulic top link, I used a 22 inch to 36 inch. So far it has worked perfectly with the Pat's Quick Hitch.
Inspired by some earlier posts on this thread (Thank you!) I decided to document the part numbers (with today's prices) that I used:
Cylinder - SPH320033 Hydraulic Top Link Cat. 1-1 with Locking Block 20 7/8” - 31 7/8” with 2 x Hoses - From Amazon - $155.99
Connectors - ADA 9250-08-08 #8 M. JIC X 1/2 IN.FEM BSPP 90 BENT TUBE ADAPTER - $35.45 each
Couplers - Yanmar Parts - COUPLER, QUICK 38 - 1A8160-48820 - $6.13 each
Caps - PER 3HDP-H3DC 3/8"H SER.CAP/PLUG - $4.067 each
The 90 degree hose connectors that I used also convert the BSPP thread to NPT thread that is used by the original Yanmar couplers. The longer size of the toplink (20 7/8” - 31 7/8) makes for a perfect fit with my box blade. As shown on the photo when the box blade is level on the ground - the cylinder is half extended. Had to turn the locking block on the toplink 180 degree around, so it would not interfere with the backhoe connector. Works great!