You should spend some time talking with a local machine shop about your options. If it was my engine I'd put aluminum heads on it since 40 year old cast iron heads tend to be a money sink. I'd also put a Holley Sniper on it rather than a carb just because that will give you fully adjustable fuel and ignition. But it is hard to convince anyone of this stuff until they learn it the hard way so I understand where you are coming from.