If the frame is straight and there's no sign of cracking at the weld, I'd assume that the repair was done correctly and leave it alone.

After all, it's had 60 or 70 years to fail and it hasn't. The truck isn't going to be hauling heavy loads or driving on mud tracks anymore. It's going to have an easy life.

Put the truck back together and just monitor the repair.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)