225 Slant Six Crank but Won't Start (Fuel but No Spark, Dist. Rotor turns)

2 Darts is assuming the OP has a points ignition. He didn't tell us or post a photo. 1970 was around the time they switched to electronic ignition. My 1969 was points, at least until I installed a Crane Cams XR700 electronic setup.

With multimeter, measure VDC from BATT- (or engine block) to coil+. Should be ~12 V while cranking, and drop to ~8 V when running. Run a jumper from BATT+ to coil+ and you will insure the coil is powered, but <5 min or the coil may get too hot. If nothing, remove the factory wire from coil- and use a jumper to touch coil- to block. Each time you lift it you should see a spark on the in-line spark tester you should have bought ($5 Harbor Freight) since you first asked. Then, see if your distributor points (or ECU) does the same as you crank.