Just so you know, 95 was the last year any Mustang received a 351W from the factory..
As far as what engine you should use..IMO, you should use the engine you feel most comfortable working on..
I like the pushrod engines myself, guess it just depends what your goals are for the car..
1991 Ford Thunderbird Sport
"If you don't know where you're going..Any road will take you there."
– George Harrison