Not to be a smart aleck... but yeah, I think I've seen it done.
Just look at a 1969/70 428 cobra jet car... or a '69 390 car....
It fits like it was stock.
The only problem could come from the 427 with the vertical exhaust bolts - I believe the hooker super comp headers can be used as they have all of the bolt patterns on the flange.
Externally the engines are pretty much the same size with the medium riser heads except for the cammer as mentioned above. The real differences are that the 427 has a shorter stroke and a bigger bore. The 428 block will not support the same size bore as the 427 unfortunately so there is no way of turing the 428 into a 427. You will hit water first. The other big advantage of the 427 is that it has the cross main bolts too so the bottom end is much stronger than the already strong 428. I have a 428 in my 70. Although its a Q code car you can do it with some work. The only difference between the small block and big block cars excluding drive train themselves is that the 428 has reinforced shock towers which I highly suggest installing if you are going big block route. You will also be able to fit super comp headers also, very tight but they will fit. They are a big pain to install but well worth it in my opinion.
Kevin