The easiest way to tell the 170 from the 225 is by looking at the thermostat bypass hose. If it's really short (like the nipples almost touch) it's the 170. The 225 had a little more space between them. If I recall, you can not change the hose on the 170 without removing the head - you can just about make it on the 225 leaving the head on. I drove Darts with both Slants. The 170 was a little slow (it was a three on the tree and those gear ratios sure are far apart) . The 225 was an automatic and it moved right along - no speed machine, but it kept up with the traffic just fine. The Dart was one of the world's all time best cars. Even though it had only four main bearings, the Slant was a near bullet proof engine. It was first built in 1959, if I recall, and was designed on a slant to get the hood line lower for a new streamlined look.
Since the motor you have is an industrial motor there could be things different than one from a car (like hardened valve seats - or not, holes drilled in different locations, etc) . It may be set up for a three point mount (one on each side of the bell housing and one at the front straddling the crank pulley. Best of luck - John