I kinda went through this a while back myself in my '61 truck, Weeds. The heads on the '65 327 I have are from a '55 283. Here's a pic of the triangle which was referred to above:
http://rides.webshots.com/photo/2111263150055391021rqhWkIHotRod, thanks for posting that diagram. That's pretty handy.
The only thing I can add to the subject other than that is if you ever replace the valve covers you will need to get one with an "offset" bolt pattern. Also, gaskets for them are not as plentiful as the others. You can find them with two holes on one side and they are advertised to fit both regular and offset. However, I found out that the holes were not placed correctly and required quite a bit of redoing. So, my advice is to take care of the gaskets you have.
