downpipe fitment is going to be problem as it passes the a/c dryer
I would also worry about the turbo being too high
and hitting the hood.
Hellion kit was designed for a 302, higher head location on a 351
might push turbo up far enough for it to hit the hood.
Also the crossover pipe and downpipe would need to be modified
Hellion makes great kits, but I think hacking one up to fit a 351
would more trouble than its worth