I just gave away a set or I would get some dimensions for you. like miracle says, just fab a set from some rectangular tubing and carry on. easy peasy. check a few frame sites and see what they use......rect tubing. welded om or flanged and bolted on.
frame dimensions and lots of other pertinent info is in here. good to download a copy
https://www.trifive.com/d1/55-59Assy.pdf