I don't think that's right, Kev.
336 and 337 got trucks from 320, 306 and 284. Pictures clearly show outside bearings.
If they were wood composite, that's what came off those coaches, but I seriously doubt they were. All three of those cars were refurbished in the late 30's. #280 has Steel Trucks, so did the others. What I think Maxwell meant to say was that 336 and 337 got old coach trucks to explain why they are not like those on 330-335.
As you know, cars 330-335 got trucks from long RPO's in 1963, and Open Gons #400-405 all got standard design coach trucks from retired short RPO's and coaches. All the Business cars kept their trucks, as far as I know.