you can just get a 4.2l crank for about 150-200 bucks and get what ever rods you want, oem or you can get forged what ever you choose. the 4.2 crank is neutrally balances thus you will need matching flywheel and harmonic balancer if you do not have a mid 01+ v6 mustang. If you are going though this trouble i would buy forged rods and pistons, and decide if you want High compression n/a or lower compression for boost later on.
finish it up with heads/cam/intakes to match you final ideal of where you want your car to be at.
with all said and done you should see 260rwhp and 280rwtq all tuned for good daily driving with an n/a motor (ive seen more just a good estimate of what you will get) and with a boosted car 300-400-500 what ever you get it will depend on the boost and what not. with a blower you will also need injectors, maf, fuel pump and what not... just an n/a motor you may not need anything, if pre 99 probably need at least injectors (maf to match)