Difference in 3 speed manual transmissions Truck/car ?????

So I found another slant six three speed manual set up from a 65 dart wagon. It does not have previsions for a floor mount shiftier. So were all the early a bodys floor shifts 4 speeds? The three speed manuals were column shift. The aftermarket offered a floor shifter for the three speed manual, but mopar did not. How do you identify the full synchro three speed? Can an older transmission be modified to full synchro?