In some situations the brackets for the original "bird leg" mounts will need to be notched for harmonic balancer clearance. The original 265/283/307 6" diameter balancer will fit the 350 crankshaft snout, but the timing mark that is secured by a couple of timing cover bolts at about the 2:00 position will also need to be used with that balancer.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!