If you're not worried about pure originality, but want to stay close, the '54-early '60s 235 is a good choice. Full oil pressure, modern-style insert bearings, and can be disguised to look almost exactly like a 216. For even more power, you could track down a 261 or GMC 248, 270 or 302...but they're more work to install, and harder or impossible to disguise.
