Definitely will not fit with the stock 69 TA Ram Air setup. The RPM is 1.5" taller than stock, and with the stock upper and lower pans, there's no way to do it.

With a drop base, you can get a 3" filter under the hood, but it's tight. You have to make sure you use a lid with the least amount of dome, and a wingnut that sits down in the center of the lid. Look through the scoops as you close the hood. You'll have less than 1/2" clearance. Good idea to use a torque chain or solid mounts to keep the engine from rocking under acceleration.

2" to 2-1/2" filter will work, but not enough air for a 400-455. Even a K&N would be borderline in this case.

Holley Street Dominator or Torker II if you can go with a single plane, or to stay with a dual plane, you can port a stock Pontiac intake. Regular old Performer is ok too.