I wouldn't say the swirl port heads are complete junk, just not much good for making upper rpm horsepower. They were designed to be used in pickup trucks, so they do make pretty good low rpm torque, probably up to about 4000. I used a set on the 355 I built for my brother's 52 chevy street rod, just a mild setup and he loves it. Of course anything would have more guts than the old straight six he had before.
Since you already have the rest of the stuff needed for vortec heads, I agree, get the vortec heads and maybe you can recoup a few bucks by selling the 193 heads to someone else.