The BLMA trucks, and the Atlas trucks with metal wheels on their most recently-tooled models (PS-1 boxcar, modern coil car, TOFC car, trash flatcar) make it much easier to lower equipment. Regarding MTL couplers, fitting #2004 knuckles in a #2001 box (or #2019 knuckles in a #2016 box) helps with the coupler height. The Barber S-2A trucks by Atlas are especially helpful in lowering transition era cars with 50-ton capacity. They aren't available separately as of yet. But with most PS-1 boxcars actually riding on ASF A-3 trucks, swapping in BLMA trucks on the Atlas PS-1 cars give you the surplus.