...For those who will install their next 351C Intake Manifold. I've been doing this trick for the last dozen 'Manifold' exchanges/experiments. I Posted this a few years back. Received acknowledgement from One (1) Person...and, have not seen it discussed here, as Yet.
Upon ready to Install Your Manifold. A Tip:
Take (4) 5/16" -18, BOLTS, 3 Inches long and hacksaw the heads off.
Screw the bolts into the 4 central tapped holes, 'Finger Snug'. Remember you'll have to un-screw them afterwards, again, using your fingers.
These four studs, now in the only true straight-up holes, will allow the manifold to be Slid Straight-Down and onto the Already Placed Intake Gaskets and End Seals/Gaskets or Silicone. Guaranteed Nothing less than an Exact Alignment, In One Try! A Blind Man could Place it Perfectly! NO offense. NO shifting the Manifold around to align the Other Bolt Holes. The Bonus here, is the studs keep the gaskets from slipping-down...Too Far.
Now, start ALL other bolts with fingers (and Don't forget the Washers)*, THEN you can remove the (4) 5/16" studs and replace with Bolts. Torque to Specs, in the Correct Pattern!
Makes the Job More Fun, and keeps the Gaskets, Covering the Ports.
* And remember...the Accelerator Cable End Mount, goes Under the Forward/Left, Bolt.