To make life as "simple" as possible, you can move all of the components from the heads-up to s/c to the n/a block, along with pulleys, etc. to end up with what we call a "top swap" setup. There's slightly more compression (9.4:1 vs. 8.5:1 in the original s/c block), but it's very reasonable and a basic tune and minor tweaks can have it running fine.
The other option is to use the full N/A engine and convert the tune to an N/A Regal file with the S/C transmission settings. There's a mix and match of items to deal with here, too, since the fuel lines need to be adjusted, and some various minor things.
Either route takes some research and resources, rather than using the same block type as a swap-in. Top swaps are fairly common, and tons of info out there, you'd just want to make sure it's running fine before sending it out the door.
Also, it was most likely the intake gaskets, since the HG's in these old iron block, iron head engines are very stable unless overheated pretty bad, or some other bad situation happened leading to that issue.
