If that's a six-axle diesel (or GP35 rear), you can use a Kadee 806 or 743 short box/short shank couplers. They mount with 2mmx8 metric screws.
You can also file/grind off about 1/8" from the rear of a Kadee 805 or 740 box to clear the coupler mounting boss on the power truck in most cases with the six-axle diesels. The GP35's rear clearance is so short that only the Kadee short-box couplers really work well.
I've used both with success. You should also get a Kadee coupler height gauge and make/buy some shims in case the couplers sit too high.
