If the weight was substantially changed as a result of the rebuilding/conversion, then the braking effort would have been cahnged to either add more braking effort to a heavier car; or less braking effort if the car was lighter (to prevent wheels from sliding). Passenger cars and engines both generally have much higher brakiing effort compared to freight cars.
If a change was required, it could have been done by changing the cyliner size and/or the brake lever ratio; niether of which may have been obvious at a glance.
Anyone have the original and converted weight for the car?