Just some questions to ask yourself...
Are you able to maintain the car, both financially and mechanically?
If you want something that is a bit more tame, in most cases, a lower HP motor will be easier to maintain. I like the 4.6 option...the beautiful thing about it is you could technically take it to the local Found On Road Dead dealer and they could service it.
Forget about going to a turbo...more hassle than it is worth, and you can achieve the same results with less penny spent on a naturally aspirated motor.
Since you live in LA, I recommend going to a local shop to build your motor if you so choose to go with a custom. The advantage is that they are here...where as KC and SA and PE are not.
I recommend two shops...Valley Ford Specialist in La Canada/Glendale (Foothill Blvd)...and JMS (I think they are in Monrovia). Dennis at Valley knows Cobras. When I visit the shop, there is always an original or two there having something done. Last week, CSX2001 and CXS3026 were in for a visit.
With regards to daily driver and something that will have some manners...couple of things to consider IMHO. First off is heat. You are in LA, so sitting in traffic is a reality. The bigger the motor, the more BTU's that will be coming off that thing. Also, the mileage will be horrible. Most bozo's who ask you about your car don't give a crap about how much HP it has...or even if it is original. They will ask how much it cost! Or like stated above, will bore you with stories of someone who knew someone who had a real one....yawn....
When they ask, and they will, you can smile and say with confidence "alot", knowing that you were smart and did not try to out pi$$ everyone else with a motor that is too much for your needs! Rather you went with a reasonable 300 - 350 HP motor. It still sounds mean, gets the job done, and is more HP than the original 289's had out the door. A motor of that size will be more than enough to get your admirers attention, and not scare the holy $hit of you when you press the loud pedal.
