Make sure you're NOT using the rubber end valley gaskets, as they can sometimes fit too tight and jack the intake up (and can also wind up squishing out over time creating a leak).
Don't go "by the book" here, only use RTV on the ends.

 

I am 100% certain you have the same issue I had. I mean everything is identical. Feel free to try another set of heads or intake. The issue is the heads.

I was able to pull the intake over enough to get the bolts started. I was pulling as hard as I could, then used the pry bar for the second center bolt.

I tried without any gaskets and had the same issue.

It's like the angle is off just a degree or two so the bolts wont start. Next time I take the intake off I am going to shave 1/16 off the top side of all 4 center bolts holes. I would have this time but I had already put the silicone on.

You really can pull it far enough if you just get a couple threads in on one side then pull that side up and over.

 

ok yeah it does seem like its off a couple degrees I just really dont want to cross thread the heads. ill try to see if i can shift it over enough to get them started. I also have a performer intake that i tried fitting on tonight and it is also out so yeah i has to be the heads.

 

The safest way is probably to drill the intake about 1/16th of an inch. Strange these are very rear heads, but I went through this last week. I was very very careful getting the bolts started and do not feel they are cross threaded.

But as I said twice before I will drill the intake when I take it off.

 

Take a look at the ost Camaro 69 made earlier. Toss the end rubber gaskets and try dry fitting the intake with just the side gaskets in place. Make sure you don't do anything more than start each bolt a couple turns, and then go to the other side and start a couple turns.
If it all fits withouyt the end seals, then pull the bolts and use Black RTX gasket maker on each end, and reinstall the intake. Like Camaro 69 suggested. I never use the end seal;s on any Chevy engine I build. I RTV them and let it sit overnight before trying to run the engine.

 

Mine didn't fit without any gaskets.

There really is something strange with the heads. The holes seem to be cut at an angle. It isnt nearly enough to fit the newer style intakes. I tried one. I actually noticed the issue when the heads were sitting on my table next to the original set. You can see they are cut strange. I set the intake on and it looked like it would fit. You can see like 95% of the threads. Its just that lat 5% that keeps the bolts from going in. If they were cast you would just force the bolts in.

 

He doesn't have the same heads as you though. If I'm remembering right, to lazy for the back button right now. My heads have been angle milled on purpose to roll the valve angle a couple more degrees. Most machine shops will tell you to bring the intake in and they'll match the cut for you. The guy that did my heads cut the intake side of the head to fit. Top notch work really. Anyway, I'm still betting on the center holes in this case. Or the gasket deal.

LOL Felpro sends the end gaskets in the kit and then says not to use them. I remember reading the paper in the bag when I was cleaning up.

 

Correct, mine are trick flow. But they are both the 23 degree angle plugs. And he said yes, the holes look 2-3 degrees off.

 

yeah i dont use those end rubber gaskets ive had some squeeze out and some that never even seal, so i always use rtv silicon. I talked to a local engine builder and he also makes chassis for race cars, his name is Matt Folk, anyways he said hes run into to this problem and he had to slot two holes so the intake would line up for some of his engines when he raced.

 

Glad to here an engine builder agrees with me. There is something about 23 degree heads. Everything was a little more work.