My 2 barrel 273 does the same.
I've rebuilt the carb, swapped carbs, changed the fuel line, all with no improvement.
I just got a small fuel pump that I will be using to prime the carb with a momentary switch.
Funny thing is my little 273 was doing the exact same thing.
Just a little puddle. Nothing at idle, just after a freeway trip.
I just "snugged" the valve cover bolts as they did not appear to be loose but
to my surprise when I put a wrench on the intake bolt it was way loose.
So I re-torqued...
I too voted weld - some time back I as well had a chebie block crack at the starter mount area.
The same machine shop that prep'd the block welded and re-tapped.