You have the best rear axle made, 9 inch, no swap. The 352 is the base for great engines like the 390, 427 and 428. It would probably be easiest to build a 390, maybe bored and stroked, down the road, if you are wanting more power. It is also a bolt in, no mods to put any of the FE engines in its place Great engine as it is, not delicate in any way. Front disc brakes for sure. The rears are probably 11 X 2 inch drum now and will not have to mod parking brake. The car as is, really needs nothing. It looks super and is. Good advise on the pertronics ignition conversion, set of shocks and enjoy. I am going to bet the gears are 3.00. Engines made good tq. My Dad had a 67 LTD, 390 4V with somthing like 2.80 gears. If you want to work up on an engine mod or swap, you can put an alum intake and carb on it. It will be good for a rebuild or follow up engine. Personally, I would make it dependable, brakes, ign, tires, shocks and enjoy. Do not cut the dash up for music mod, please.
Leave it stock. Great looking car. If it was a hard top id say go for it but the vert just makes it look sweeter sitting stock. I could see the disc conversion to make it a bit safer in the braking department but other than that id stick to how it looks now. Classic.