modifying C frame motor to use on Jhead?

I have a new 184 frame 3hp motor which I want to use on a Bridgeport J-head. The head it's going on had a real bastard of a motor on it: wasn't a C-frame, the
guy sawed off the rigid mounting legs and mounted a 10" disk of aluminum to one end via the 4 end bell screws. The motor was 3450 rpm and ran the head too fast for general purpose use. I picked up a new 1760rpm motor which is a C-frame. I know a 10" circle of metal can be used as the base, since the last motor was set up that way. I was just wondering if anyone knew the dimensions of the 2 motor hold-down bolts on the thing, or knows what the bolt pattern on a 184C frame is.
GWE
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When I converted my Bridgeport clone with a C-frame motor, the motor shop where I purchased the motor had a cast aluminum conversion plate in stock that fits the motor and has two holes that are in the correct position for the motor hold down/adjusting bolts. Here's a pic of the installation:
http://albums.photo.epson.com/j/ViewPhoto?u 51254&a489737&pQ714279
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Google for "motor nema frame size chart"
http://www.electricmotorwarehouse.com/NEMA_frame_info.htm
i
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Grant Erwin writes:

http://www.truetex.com/dcdrv.htm http://www.truetex.com/bridgeport-dc-drive-motor-plate.pdf
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