I have a 70 ford 300 I6 that was rebuilt a few years ago thinking about putting in my jeep when my 258 crashes. I was told a mustang 5.0 bellhousing would make the 300 adapt to my t-5. this motor does not have power steering, would it be difficult to rig something? Good Idea or Bad?  

Interesting! I do not believe I have ever heard of this one. Power steering would not be hard to do with a little bone yard time. My concern is if it is longer and taller than 258. Otherwise It sounds like a interesting swap. Since you have a pre-emission 300 it should be good and strong too with lot of low RPM torque  Just for the record, all AMC 6's and V8's since mid 70's have same bolt pattern on bellhousing so if 300 will no fit, any AMC engine mentioned above will go it with little fuss.  

I found a site that has deminsions of both motors it is pretty close length and width and high but the sump is in the front on the 300 and rear in the 258 so my concern is clearing the diff.any suggestions? or just stick it in see.  

Look for a 300 pan with sump in a different location. It is not unusual to have different sump locations and different applications. All it takes in a different pan and pickup tube.