Bowtie blocks typically have a bowtie insignia cast into the side, just above the oil pan rail. Also, most have blind head bolt holes (if you have the engine apart) with the exception of production 502 blocks which have the bowtie on the side, but not all have blind head bolt holes.
Thanks for the info. I was wondering because I have the bowtie symbol cast into the block but it is a 502. It has Pass Hi Perf cast into the front of the block as well. I do believe that the head bolts are blind holes not through into the water jacket.