Ford NEVER made a straight-8 engine, only V-8s.
Boosting the old engine with moderate boost (5-6 psi) shouldn't be a problem at all. Pistons are much heavier and thicker if aluminum, and may be cast iron. The crank and rods are forged steel, cast wasn't strong enough until techniques were developed around 62-63. The cylinder walls are thicker due to casting techniques not developed until the early 60s for thinner blocks. Everything is tough enough, but you do make a good point of making sure everything is in good working condition or better yet newly rebuilt. Detonation would be a concern, but that would be the case on a modern engine. Cast iron pistons might not be tougher than cast aluminum -- heavier an thicker, but also more brittle.