How you going to make a 327 4 bolt? Lots of machine work = $$.
Probably cheaper to start with a 4 bolt 350 and make it a 327. Check the crank. There are 3 "IFs. First smack one of the counterweights with a hammer. #1 If you get a dull sound it's cast iron. Save it for grandmas caprice. #2 If it rings, it's forged steel and you can proceed. #3 If it has the medium size journals, all you need is a medium journal, 4 bolt, 350 block and your'e in business. Go to MorTec.com to get journal specs. Keep in mind that a 327 with lots of mods, will develope 400 HP at somewhere close to 9000 RPM. A strong bottom end is a must, along with a super strong valve train. One more if: If you twist it that tight, eventually it WILL fly apart. Been there, Done that, and I'm not alone. One last if: If you blow N2O in it, it's going to fly apart sooner. But the fun is what it's all about right?