hello, there is no harm in upgrading to even larger injectors like the 740cc size. We always recommend 740s for anyone really as they provide excellent idle characteristics (Nismo). Late style Nismo injectors feature multiple holes for fuel spray. The DW injectors may require some tuning to get them to idle smoothly but will work. In either case you will need to get the adapter kit like you mentioned or 300Degree rails to make them work. Your best bet would be to buy from one of the sponsoring vendors on this site. If you have any other questions feel free to shoot me an e-mail.
