Howdy Jisham:
The 1st and best thing to do is to put together a plan that includes a realistic budget and times. The plan should include your needs for this car for daily transportation as well as your mechanical abilities. It will be much more cost efficient in the long run. Even if you can't do it all at once, choosing the pieces and purchasing them in a logical order will save you money in the long run. So, what is your goal when you are finished with this engine?
In general, it is best to build the block first, as a foundation. It is most labor intensive and most technical with parts and parts coordination, specs and measurements, machining and balancing. Details such as achieving zero deck height, selecting the cam and balancing are not as glamorous as a header, but are critical to a good and long running engine.
For example, If you plan to use an Aussie or the new FSPP aluminum head, it would make little sense to get a D8 to modify. On the other hand, Mike's alloy baby would be overkill for a daily street driver(IMHO).
If your plan is to stay with a log type head, upgrading to a '76 and later head is a good place to start.
So, what's your plan? Enjoy the journey.
Adios, David