These one's...78500, correct?
Engine Performance & Vehicle Customizing Products From Hedman | Hedman Performance Group
If so......I put them on my '73 Duster ('71 clone), 340/4 speed, power steering & mini starter. Passenger side goes on without a problem (like usual). Drivers side, I removed the motor mount bolt and jacked up engine from underneath a couple of inches.....bolted them on, dropped engine back down, replaced motor mount bolt.
I forget why I had to jack it up......most likely ease of installation, as I put them on laying on garage floor. :icon_fU: