what's the problem? Why would it be a bad idea? Just make sure your floats are set (have to do that w/ a 4bbl), then make sure your distrib is clocked right, fill the primary bowl up, turn the mixture screws in all the way then out 1.25 turns, turn the idle screw down (so the engine mantains about 2k) and let her rip. Once it's warm turn the idle up to 22-2400 set your timing in full around 36* (vac advance pluged) get your vacuum gauage out and tune for best signal. Once the 20 minutes are up, change the oil and go for a drive. You can leave the outboards un-hooked if you like, but they aren't going to open until your engine goes under "load"
As for cutting the block or heads, sure but make sure the intake will seal before you fire it. If you cut the heads a bunch you'll have to have the intake cut too. I had to have .030 taken off a brand new RPM once.