58 up cars used center mounts on the engine with a mount on the rear of the trans on both the 235 and V-8 applications.
Passenger cars used the X frame through 64.
Since the newer style 230/250 engine was used in 63 up cars it seems likely to me that the mounts from a 63 6 cyl or V-8 should work on the 58 as well.
Fred
