I've done the swap also, and stock type valves cover height wont hit the booster, but anything taller will. You can replace the booster with a late model smaller booster and it's a direct bolt in.
The radiators for a big block Camaro are all top and bottom mount, and you can simply relocate the rubber on the bottom, then buy the wider top for about $24 for a chrome top. You'll need to open up the core support to allow more air to the wider radiator, but I think you'll find Chevy stamped a ridge in the sheetmetal so you can simply cut along the ridge with a jigsaw or sawzall.
I modify the heater boxes the same way by removing the box and flipping the core 180 degrees. I also cut the heater box in half while it's off and tack a sheetmetal strip over the cut so future removal of the core is a 10 minute job, not an all day job.
I've always used the stock smallblock motor mounts, and if you use them with the shorter valve covers you might not have to do the heater core swap. This picture is with small block motor mounts on engine and frame, stock booster, original heater core, and the 427 in my '71 Camaro. I actually had to trim the fins off my Edelbrock valve cover on the pass. side rear to keep them from digging into the heater hoses. The booster is close, but I can still easily remove the valve cover.