i personally like EFI better, simply because while other guys are under the hood changing bleeds and jets i'm sitting on the starting line like LETS GO! the ECU controls timing, but most guys switch to an MSD. injected 5.0s respond very well to mods... my car (89 LX 5.0 auto) is bone stock, and it's still pretty quick... and they sound great if you just remove the mufflers and tailpipes, i would know. stock auto 5.0s are typically low 15 cars... if i were to do H/C/I/E/G on mine, it would probably go high 12s, all for less than a couple grand if you know the right people. that's a pretty serious street machine for the non-hardcore. all years of mustang were available with manual trannys. all foxes except for the 4-speeds use a T-5 or an AOD. the SROD-4 isn't a very good transmission, i wouldn't use it personally. it was only available for a few years if memory serves (there was one in my '86 notch 4banger). expect to pay anywhere from 500 to 2000 dollars for a decent, running foxbody. i paid 800 for mine, simply because the seller was desperate for cash, and i lucked out... perfect interior, motor runs great. my 86, which is now gutted, cost me 300. insurance should be around 100/mo. and most guys keep their efi.
hope that helps.
andy