I highly recommend round tires. Flat spotted ones are kinda bumpy.
More seriously, I have been spending a lot of time trying to decide what tires we will buy for our future replacements.
We have been racing on 225/40r14 Toyo T1Rs. They are short and fat and reasonably grippy. They are discontinued and while I can still find some, they are going to be old-new tires.
As ifb_mole pointed out, your wheel size will affect your options. I currently have 14" or 15" wheels so the options are pretty limited and if they have a tire for that wheel, it will typically only be 1 size.
I have some adapters and 17" wheels I can run now but I am working on a 5 lug conversion without adapters. You start getting better tire options once you get up to 16" wheels but 17" seems to be a good sweet spot. Some performance tires start with 17" so you get way more options.
Falken Azenis are pretty much a staple tire in Lemons. They have mixed reviews. They have reformulated the rubber for 2010 and the new compounds will be RT-615K. I am not sure when they will be available.
The Hankook RS2 has been very popular but is discontinued.
The Dunlop Star Spec Z1 is probably the grippiest tires we can run. No personal experience though. I've had mixed reviews on that tire too.
The reality is we are racing on street tires. Many tires will perform well if you do not overheat the tires. I am trying to come up with a solution to keep the tires cool. I am thinking a bigger tire, probably shaved, will stay cooler and therefore perform better and last longer.
I spent a good while on the phone with a guy at Tirerack last week. He discouraged the Star Spec. They have many knowledgeable people there that can probably offer you some good advice.
Troy
#35 LRE
1973 Datsun 240Z