Since it's a 69, if that's the original engine there'll be a partial vin on the front of the block down low on the passenger side.
Also, check the block date code and block casting code:
If you have a 69 block (the date code above will tell us for sure), that XH on the front indicates it's out of a Grand Prix, but otherwise will be equipped the same as the GTO engine (which would have been coded YS).
You already have the best available intake for a moderate street Pontiac. You can save weight with an aluminum manifold, but you'll give up power to do it.
The XE268 is a decent cam in a 400, but you can't use stock springs with it. You'll also have to replace the factory rocker balls/nuts with fully adjustable pieces (poly locks), and if it were me while I was at it, I'd replace the factory bottleneck rocker studs with stronger 7/16" ones. Factory studs have been known to break at the bottleneck, especially with "stronger than stock" valve train components.
Since the heads are going to have to come off anyway (to have the spring seats cut for taller valve springs), be sure and cc the chambers and check piston deck clearance. Assuming all the dimensions are "nominal", that motor's going to be just shy of 9.6:1 compression which (in my opinion) is a bit much for 93 octane fuel and iron heads. Since you've got manual brakes and don't have to worry about vacuum to run the booster, I'd be tempted to go with a little more
cam or maybe a wider LSA (or both) to try to manage cylinder pressure and stay away from detonation. You're going to want to make sure you cooling system is top notch, and double
sure it never runs lean.