I took my 340 Dart out for a real test drive.

It only has about 70 miles on the motor.

It was running strong but after about a 50 mile loop it started to buck...overheat....and the oil pressure almost pinned the gauge on high.

I nursed it back to the garage and noticed white smoke coming out of the tail pipes. When I re-started the motor...it acts like it has a terrible miss and rocks like crazy.
The oil isn't milky on the dipstick.
There is seapage of something coming from the bottom of both heads visible on the front of the motor.
I did not re-touque the heads soon after I got it started. I have been told I should have done that after the initial startup.

with this information, are these symptoms of a blown headgasket or could it be something else.

thanks again guys.