i would find an engineering workshop and get their input, my gt rts cracked around the steer tube, my local engineering firm is going weld the cracks and they seem to think there wont be any future problems. I wanted to replace the steer tube with a new tube, but no one was interested, so had to go with the welding option, but i did speak to 3 firms and they all said the same thing.
one guy on here replied to my thread and said his friend had the same bike as you and that had cracked, he got the cracks welded several years ago and has had no problems since.
lets be honest you cant have a bike like that just to stick on the wall and look at, after all if you find the right people most things can be repaired.