I purchased a Titan S-200 hydraulic plow w/ 1/2 " flat faced couplers. The Titan 3/8 hose was equipped w/ 1/2" increaser bushings. Just keep the titan 1 /2" male iron pipe thread and reduce it to 3 /8" . Remove only the flat face couplers, titan furnished one male and one female.
My Kubota remote came w/ Pioneer 8010-4 male 1/2" and 4050-4 female in 1/2" I do NOT know if The 8010-4 remains The same for The 3/8" male with just The size change. I use all 1 /2" fittings on 3 /8" hoses w/ bushings.
The bushings, to increase of decrease came from tractor supply, surplus center has them as well. (For My other attachments)
My Pioneer Ag fittings are push/pull type, NO collar or sleeve to pull back to lock.
The flat face removed fittings are just surplus . Titan actually sells Ag fittings also, saw them on amazon, but can be purchased direct, shipping free.
Do NOT use iron plumbing fittings to change pipe thread sizes.
Also the cylinder stroke on my plow is very short. Suspect the same on your grapple. Once connected. Open the valve SLOWLY, or the cylinder may SLAM to the open or close position. Mine Did and at an idle!!