There is also something called a Structural Rib Bolt, manufactured by Bethlehem. It has a round head which looks like a rivet, but the shank is ribbed and threaded. They are installed like a bolt, and the nut is run on with an impact tool. They are available in a variety of lengths, and I have used them to good effect in place of hot rivets. They were designed to replace hot rivets in bridge and structural applications, so this might be a good compromise.
As to the post about the Friends of the East Broad Top preserving EBT rolling stock, that hasn't happened yet. There are way too many hopper cars sitting around, many of which were awaiting shopping in 1956 when the railroad shut down. The better cars have been sold over the years, and only the really used-up stuff remains now. Besides which, the FEBT does not have to same relationship with the owners of the EBT that the Friends of CATS has with the railroad.