Looks like a slipping clutch to me
Your is RPM going up but your speed is almost static.Definite slipping issue regardless of tranny MT or auto

 

It can't be a slipping clutch because this just popped up when I got my engine swap. And my RPMs aren't rising look again and you'll see it stays at about 4,500. It has to be something that was changed when the engine was put in.

 

I suggest you check the physical throttle linkages if you haven't already. The accelerator pedal on these cars should not be hard to push. Maybe something is binding. There is a cheap spring under the gas pedal assembly -- it is seated correctly and not limiting pedal movement?

 

I'll check for any conflicts with the cable today.