Well, I'll give you my $02 and then everyone can educate you by telling you where I'm wrong.
You've posted in the FE forum, so my comments are FE related. Depending on the thickness of your wallet, that can range from a nice 390 or 428 to lots of bucks in a stroked Shelby arruminum motor or beyond. Southern Automotive appears to have got its price on 427 FEs down to around $15K (someone correct me if I'm wrong). You should be able to do a 390, or preferably a 428 (some Cobras came with 428s so they are correct) for around $10K or less depending upon their condition and what items you want. My Shelby has been Velasco-stroked to around 484 ci and has all the good stuff...$25K. Lots of variables. They will all kick some major ass. George Anderson will build you whatever you want. My own builder, Joe Boghosian, can fit a nice 7500hp AA/fueler motor for you if you are REALLY into acceleration.
Top loader? Go to David Kee. I've got a wide ratio, big in/big out. He's getting ready with arruminum cases down the road. Some folks like a five speed...Tremec II or Jerico (different mounts needed).
3.31 gears in mine have been a nice combo...good cruising speeds and tons of acceleration. The big motors do fine with wide ratios. You can go with 3.54s, but you'll want to consider a close ration or a five speed setup. The Kirkhams will tell you that 2.88s even work nicely...big power/low weight gives you those alternatives.
Just have a ton of fun!
