Depends on your mods. If you plan on going e85, the 120's carry cars deep into 10's. if you plan on going race gas or pump gas and alky, that can be done with 60's. i have 60's with very few mods and the car ran great till i waxed my turbo.
I'm having my ecm modded so i can bump up to 120's (shipping it to bob bailey tomorrow - excited!). I will have my 60's (along with corresponding 93 oct chip and e85 chip) up for sale as soon as i get the ecm back, get new injectors, turbo, downpipe, powerlogger, wbo2 all installed. Come to think of it, it may be awhile!
Bottom line, 60's are a good start; but it will depend on your goals with the car. Injectors aren't really cheap so it'd be beat to buy 'em once.