buying a Colt M4A1 from my LGS for $800 after tax (I work there part time so I'm getting a deal regular customers wouldn't get)

Want to ditch the stock furniture and clone a military rifle. Was thinking about cloning a Marine-issue M4A1 (because I was inna muhreens) but have been thinking about cloning a block II with the RIS II FSP.

If I went with the Block I, I would probably opt for a Troy handguard as KAC rails are unobtanium. If I went with the Block II, I'd have to fuck with removing the FSB and putting the RIS II on there.

Who has experience with both and could give me their recommendation.