Almost anything can be done, and has been done to get an old Chevy going again. On my latest 50 3600 with the original 216 and probably original fan, I noticed the blades were cracked near the rivets that join the two pieces together. I only realized that when I replaced the water pump. I had a fan from 58+/- 235. And the center hole was too small to go on the shaft of the pump. So I fashion a simple jig to keep my hand drill centered on the existing hole and cut a larger hole with a hole saw. Worked great. As best as I can recall I did not have to drill new bolt holes. That was 11-12 years ago so I may have... I did have to tweak the blades slightly to clear the balancer, but other than that it all worked well.

Professional Novice