11:50's on motor is a tough nut to crack, especially when conditions are hot or humid.
Forged or cast crank don't really matter, one is just about as good as the other. Good piston/rod combos are easier to find for a forged crank though.
As with most any motor headwork is the key. A Slant is tricky, because it is very easy to overport the head and all that does is creates reversion problems. It is also easy to put too big of valves in it, The small bore really shrouds a big intake valve.
Compression needs to stay around 11.5ish or it will eat head gaskets like crazy.
Cam is pretty critical too. Too much and it's a pig, too little and you leave a lot of power on the table.
Alcohol is almost a must too.
A rollerized 904 is almost a must for that fast unless you run a stick. A stick can be worth almost 1/2 second, but consistency may suffer and breakage will visit often.
As everyone has already said, you need a LIGHT car. 2000-2100 would be ideal, but hard to get to without a tube chassis car or a 61-62 Valiant/Lancer.
Finding little things that will get you a couple hundredths here and there will become a passion. Your weather station will be your best friend and worst enemy on the same day.
Plan B is build a fairly stock motor and turbo it. Consistency will suck, but it will be rocket fast and relatively trouble free when you get it dialed in.
If you're like most of us Slant racers you will follow plan A, and then wonder "Why in the hell did I ever do this when a smallblock would have been easier and cheaper?".
