Welcome to the board and enjoy your project but more importantly the time with your Dad. It will mean a lot to him now and you later.

As far as the 340 they produce good power in stock form, first and foremost build a strong bottom end and work from there. I would however make sure you use flat top 68-69 style pistons (I liek forged)and not the dish style from the 70s. I would go with a little over stock camshaft from what yo implied you want, someone else may have a particular number to suggest, most cam manufacturers will have suggestions (I like comp cams). Use good cast iron heads, Js or Xs, with a competition valve job and mild to moderate port work. Consider a LD340 intake or similar dual plane with a Holley 650 area double pumper for 4 gear, vacuum secondary for auto. I like a unilite, but the stock electronic distributor is a good unit with the performance upgrade. Make sure your exhaust is good enough all the way out the back to let it breathe properly, an engine is nothing more than a air pump and you have to be able to get the air out to get it in.

One of the most important items/chooses in my view on an enjoyable street car is the gear, a 3.55 is a great all round gear, maybe 3.23s on short tires or 3.91s on tall ones.

Understand your build will probably change as you go through it but keep a basic theme and you wont blow as much money.