Sometimes with these engines we cause more damage opening them up than if we left them alone. Not saying that will be the case here, but just something I have seen happen before. Even changing to a detergent oil can cause problems in these as the sludge starts coming loose and they also start burning oil.
But, to answer your question. If the engine has been running well and no odd noises, you can probably just clean it up, maybe change the oil pump, and button it back up. What oil have you been running in it? If you don't have a history on it, I would not change to high detergent oil for the reason above.
The final determiner though will be how you intend on using the car. Around town use is one thing, but long trips from home are another. You can probably clean it up as you described and it will last a long time around town, but you may not want to take it on long trips without a proper rebuild.
If carbon in the heads, valves is a concern, Mercury Marine sells a product called Power Tune. You bring the engine to a fast idle and spray the entire can down the carb, and let it sit with the mixture in there. We let them sit overnight at work, and the next morning when you start it up all this crud comes blowing out the exhaust. I use it on my T because it runs rich and carbon builds up.
Don
