ALL 1970 B body AM (and AM FM radios) are the same. Their is no diffrence between a rallye dash or non rallye . They all use mounting bolts on the front . Trust me, I have handled more 2884752 (and 2884753)radios than anyone on the planet (just finished converting one to 180 watt stereo just moments ago as a matter of fact) The 70 AM was manufactured by both Bendix and Phillips, but I can assure you , none had threaded knob shaft protrusions .
Here is one for refrence ....

Greg



http://wardsclassiccarradiorepair.com/