Frames for big twin flatheads

[John m kelly]

Hello is am starting a build on a 1937 big twin Harley flathead. I do not have a frame but plan on buying a replica model. My question is where the flathead and knucklehead frames interchangeable during those years when both engines were available. If I chose a 1941 frame say would the 1937 motor fit. I know that the top motor mount is different for those engines but is the frame mount the same.
Thanks J Kelly

[vph-d]

BTSV and OHV frames were the same.
VPH-D

[John m kelly]

Thanks for the reply, that is what I thought.

[knucklehead 61]

1937 & 1941 frames are very different though.
rake is different also.

[exeric]

If I chose a 1941 frame say would the 1937 motor fit. Thanks J Kelly

Any Knuck motor will fit in any Knuck frame, and Pan, or Shovel frames with a spacer. It's Pans, and Shovel motors that won't easily go into a Knuck frame.