No they are not a direct replacement. And all the ones that are easily available now are dry sump. The only after market heads available for the 4.3l are Brodix Lil Brodie which early 4.3L intakes fit and a few Bowtie heads which require complete custom all the way around.
disturbing V6 is correct on the blocks. Part # 10134387 is the only street Bow Tie performance block made. I'm not even sure it's factory available any more. Possibly only on the used parts market. It is or was cast iron though. Could handle up to a 4.180" bore and a 4" stroke. The aluminum Bow Ties were only dry sump.
I just sold a set of 23 degree Bow Tie heads listed in the Classified section that were a nice improvement to Vortecs. They had bigger valves and ports and could be adapted to a Vortec manifold by drilling holes in the heads for Vortec mounting. They used small block Chevy valve train parts....valves, springs, rocker studs, and rockers. Surprisingly enough, the heads were the same high port design as the Vortecs leading me to believe they were a perfect example of the racing industry driving technology for the street. The part number is 14044883 and 14044884 depending on assembled or bare. You can still find these heads from time to time. I see a couple of sets on ebay every year. No modification to the short block necessary but I would think that if you bothered using these heads, you would do a full build to get the most out of them.