Looking good so far, only done it twice? Hard to tell from the pic but the booster doesn't look like a Hemi booster with the brackets that lift it up and out of the way of the cover. I swapped a 472 into a 70 Challenger last year and it fit great! Only problem was getting parts out of Newcombs!!! That's another story though.
The booster in the pic is one that I bought from either Jim's or Jack's on the internet. It is supposed to be the closest one to the hemi version available at a decent price. I wasn't sure if it would clear without the offset bracket so I tried it. No way will it clear. The only company reproducing the offset bracket is dayclona and they're $425. I've seen those boosters that narrow down and clear the hemi valve covers without using the offset bracket. I really though that I was getting that one when I ordered the one that I have now.
I also bought a setup from one of the hotrod companies on the internet that is supposed to be a bolt in deal for e-bodies. NOT !!! You have to alter the rod going to the brake pedal since it's about 2 inches too long. It also uses different size brake line fittings than stock. It has the offset bracket and will clear the valve covers easily so I'm going to cut the rod down and tig it and reinforce it so that it will work. I'll just use the other booster and master cylinder on my superbird clone.
As for Newcombs, I've read a lot of stuff about the nightmares of trying to get anything from them so I didn't even try.