How well a 351 fits in an SN-95 (or fox for that matter) depends on the combination of parts added onto the 351 shortblock.
Heads, Intake, Headers maybe a poweradder... etc.
For instance, TFS Highport heads will make off the shelf header selection a nightmare on an sn-95 if you choose to keep the sn-95 bellhousing.
Do some searches, it will SAVE you cash by learning from others trial and errors.