motor bracket sizing?

[James Reichman]

I came across 2 "old iron" machines. For a really sweet price. They both are three phase. I would like to convert them to single phase by changing the motors. One is a Rockwell Heavy Duty Shaper built in 1951. The other is a powermatic model 100 12" planer. They both ran sweet when I picked them up. I have removed both motors and switches. And I'm in the process of cleaning them up. On the old motors both part numbers begin with the #184. I'm thinking that is the nema motor size? I would like to put back in 3hp motors in both (that is what was in there). I found a place online that sells "motor mounting brackets adj." I'm looking at motors and the budget is a little tight. So my question is can I run an adjusting bracket for say a 184 and throw in another motor with all the same sizing except the mounting bolts?
The place that sells the brackets will be getting a call with the questions. But figured i'd run it past the experts:D. So what do you think?