Re: New Build (raw engine)
This will work!
Form the bracket as shown...you can use a piece of pipe that is close to the frame size as a mandrel.
I think you can get automotive type muffler clamps as small as 1 1/4"...If not use a cable clamp, Home depot etc. has them.
You'll have to fuss around with it a bit to get it just right, but it will be strong.
Don't worry about forming it perfectly to the frame, just get it close. The clamps will draw it up the rest of the way.
You can use rubber sheet, home depot, between the bracket and frame if you need to correct the spacing.