Yeah, there are a lot of specific parts required to simulate an original Ram Air set-up. Unless your car was a factory Ram Air car, it is not worth doing. IMO
I've read that, from a performance standpoint, the Ram Air set-up added very little performance. I think this is due to the fact that the scoops are too small, too far back, and too close to the hood. Now, the early Firebird Formula Ram Air scoops are a different story.
I think your '70 has the same hood as my '69 RA3 had, less the Ram Air. Besides the open scoops, there is a pan that bolts to the underside of the hood. Then there is a special air cleaner, with a foam seal, which seals off the Ram Air pan and directs the air into the air cleaner. I'll look up some good links and try to also post some pics, later.
Now a Ram Air 3 engine is not too terribly hard to simulate. But, if you try to get all the exact factory parts, with the correct numbers, then it will be VERY costly. But, you can get the RA3 performance, without having all the matching numbers.
According to the Wallace site, the '70 RA3 engine had #12 heads on the manual trans engine, and #13 heads on the auto trans engines.
The block used for all, was the #9799914.
The manual trans Q-jet was #7040273--the auto trans Q-jet was #7040270. Again, this is according to the Wallace site. As Pinion head has pointed out, there is a lot of wrong info, online.
Anyhow, I think all the '70 RA blocks were 4-bolt mains. And these blocks sell for much more than they are worth, unless you are doing a numbers matching high dollar resto of an original RA car. IMO. But, it looks like all '70 400's used a #9799914 block. So, a non-RA block would have the same casting number as a RA block, but a different 2-digit code on the front. A later #481988 block is plenty good for even a high hp build. BUT, they are not numbers matching.
It appears that all '70 400 GTO engines, with auto trans, used the #13 heads. So, any '70 400 block, with #13 heads would LOOK almost correct, for a RA3.
Now, for the Q-jet. Again, a RA Q would be quite expensive. But, there are quite a few '68-'70 Q's that LOOKED very similar to the '70 RA Q's.
Now, for the inside of the engine: You obviously can't see any internal parts. But, if you want a similar cam, any of the 068 grinds would be similar. The Melling SPC-7 is an example. The RA3 had cast pistons and rods. But you can build it with forged pistons and rods, and most would never know.
So, I reckin the bottom line is that it just depends on how original and numbers matching you want your RA engine and set-up to be. The more original and numbers matching, the higher the cost.
1970 Pontiac GTO Judge RAM Air III System Complete RARE | eBay
1970 Pontiac GTO Trans Am Firebird RAM Air 400 Carburator | eBay
1970 Pontiac GTO Trans Am Firebird RAM Air Manual Carburator | eBay
RM-2 D-Port Ram Air Style Factory Headers 68-72 GTO and 2nd Gen Firebird/TA